AI Agents, MCP, and the Modern Framework Landscape

From agent fundamentals to the framework ecosystem and a practical implementation plan for exposing your internal tools via the Model Context Protocol (MCP).

How AI Agents Work
Tools Are Semantic Contracts
Patterns: From Workflows to Full Autonomy
The Framework Ecosystem
Multi-Agent Teams
Reference Architectures
From Zero to Production: An Implementation Plan

How AI Agents Work

An AI agent is an LLM-driven system that operates in a loop:

Plan — decompose a goal into sub-tasks.
Act — select and invoke one or more tools.
Observe — read tool results and update internal state.
Iterate — repeat until the goal is met or a stopping condition is reached.

The most foundational example of this loop is ReAct (Reasoning + Acting). Introduced by Yao et al. in 2022, ReAct interleaves chain-of-thought reasoning traces with action steps — the agent thinks out loud about what to do, calls a tool, observes the result, and reasons again. It is effectively the “Hello World” of agent architectures: nearly every modern framework (LangChain, Semantic Kernel, ADK, Agents SDK) ships a ReAct-style loop as its default agent mode. Understanding ReAct is the prerequisite for understanding everything else in this article.

Optionally, agents incorporate memory (short- and long-term context) and human-in-the-loop checkpoints for safety-critical decisions.

NVIDIA’s canonical decomposition remains a useful mental model:

Component	Role
Agent Core	LLM reasoning engine that drives the loop
Memory Module	Persists context across turns and sessions
Tools	External capabilities the agent can invoke
Planning Module	Strategy selection, task decomposition, re-planning

Agents vs. Workflows (Anthropic’s Distinction)

	Workflows	Agents
Control flow	Hard-coded DAG	LLM-decided at runtime
Predictability	High	Lower — higher variance
Auditability	Straightforward	Requires tracing
When to use	Known, repeatable processes	Open-ended or exploratory tasks

Both belong to the same agentic systems family. Production systems frequently combine deterministic workflow steps with agent-driven sub-tasks where flexibility is needed.

Tools Are Semantic Contracts

Tools are semantic contracts. An agent reads a tool’s name, description, and schema to decide whether and how to call it. If any of those signals are vague, the agent may:

Call the wrong tool.
Pass malformed inputs.
Misinterpret outputs and hallucinate downstream.

Anthropic’s research on writing tools for agents shows that treating tools like developer-facing products measurably improves completion rates and reduces token waste:

Principle	What It Means in Practice
Strict schemas	Typed inputs/outputs with required vs. optional fields clearly marked
Helpful truncation	Large payloads are summarized; callers can request detail on demand
Clear error hints	Error messages tell the agent what to do next, not just what failed
Namespacing	Tool names scoped to a domain (e.g., `legal.searchCases`) to avoid collisions
Pagination	Bounded result sets with cursors, preventing context-window overflows
Evaluations	Automated test suites that measure agent success rate per tool

Patterns: From Workflows to Full Autonomy

These patterns sit on a spectrum from fully deterministic to fully autonomous. Choose based on the level of control and variance your use case demands:

Pattern	Description	Control Level
Prompt Chaining	Sequence of LLM calls; each step’s output feeds the next. Optional quality gates between steps.	High
Routing	A classifier directs input to specialized prompts or tool sets.	High
Parallelization	Multiple LLM calls run concurrently — either sectioning (split task) or voting (same task, consensus).	Medium
Orchestrator–Workers	A manager agent dynamically decomposes a task, delegates to worker agents, and synthesizes results.	Medium–Low
Evaluator–Optimizer	One agent generates; another critiques; the loop refines until quality criteria are met.	Low

Rule of thumb (Anthropic): Start with the simplest pattern that solves the problem. Escalate to full agent loops only when the task genuinely requires dynamic decision-making.

Real-World Example: GitHub Copilot in VS Code

GitHub Copilot’s coding agent in VS Code is a good illustration of how these patterns combine in a shipping product:

Routing — When you type a message, Copilot classifies intent: is this an inline completion, a chat question, or a multi-file edit? Each routes to a different pipeline.
Orchestrator–Workers — In agent mode, Copilot receives a high-level task (e.g., “add input validation to the signup form”), breaks it into sub-tasks, and delegates each to specialized tool calls: read files, grep for symbols, run terminal commands, apply edits, run tests.
Evaluator–Optimizer — After making changes, the agent runs linters, tests, or type-checkers. If something fails, it reads the error output, reasons about the fix, and iterates — a generate → evaluate → refine loop.
Prompt Chaining with gates — Each step’s output gates the next. If a file read returns unexpected content, the agent re-plans rather than blindly proceeding.

Under the hood, this is a ReAct loop backed by MCP-style tool integration: Copilot discovers available tools (file system, terminal, search, editor APIs), calls them via structured schemas, observes results, and reasons about next steps. It is a concrete example of a production system that blends deterministic workflows with agent-driven flexibility.

Copilot also lets you swap two key levers that directly affect behavior:

Model — Switching from, say, GPT-4o to Claude Sonnet or Gemini changes the reasoning engine. Different models have different strengths: some are better at planning multi-step edits, others at following instructions precisely, others at minimizing hallucinations. The same tools and the same prompt can produce noticeably different results depending on the model — which is why evals (Phase 4 in the implementation plan below) matter.
Mode — Copilot offers three built-in modes that sit at different points on the autonomy spectrum:
- Ask — a question-answer pipeline (prompt chaining). No file edits, no tool calls — just reasoning over context you provide
- Agent — the full orchestrator-workers loop. It can read your codebase, run terminal commands, install dependencies, create files, and iterate on failures autonomously. This is the ReAct loop in actionPlan — a middle ground. The agent reasons through the task and produces a step-by-step plan, but waits for your approval before executing any changes. This is essentially the “human-in-the-loop checkpoint” pattern described earlier.
Moving from Ask → Plan → Agent increases flexibility but also increases variance, cost, and the importance of good tool schemas. You can also define Custom Agents with tailored instructions and tool sets — effectively creating a specialized routing layer for your own workflows.
Sessions — Copilot supports running multiple agent sessions in parallel, each with its own model, mode, and context. This turns the single-agent model into a practical parallelization pattern: you can have one session writing unit tests for a component, another implementing a new feature, another generating documentation — all running concurrently against the same codebase. This works especially well in architectures with clear module boundaries. In a Django project, for example, each app (authentication, billing, notifications) is largely independent — its own models, views, URLs, and tests. You can safely spin up parallel sessions scoped to different apps with minimal risk of merge conflicts because the file surfaces barely overlap. The same principle applies to any codebase with well-defined package or service boundaries (microservices, monorepo packages, Go modules, etc.). In practice, parallel sessions let you trade wall-clock time for throughput — compressing what would be sequential work into concurrent work, as long as the tasks are sufficiently isolated.

The Framework Ecosystem

The ecosystem splits into three layers. Agent frameworks are where you build agents. MCP is the protocol that connects them to external tools. Governance layers manage fleets of agents at enterprise scale. They are complementary, not alternatives.

Agent Frameworks

Microsoft Agent Framework

Currently in public preview (GitHub).
Unifies Semantic Kernel (SK) and AutoGen under a single programming model.
Adds typed, graph-based workflows with strong observability (built-in OpenTelemetry).
Native MCP and A2A protocol integration.
Multi-provider support: Azure OpenAI, OpenAI, Anthropic, Ollama, and more.
Ships with a developer UI (DevUI) for inspecting agent traces.

OpenAI

OpenAI’s agent stack is split across several products:

Product	What It Is	Launched
Responses API	API primitive combining Chat Completions simplicity with built-in tool use (web search, file search, code interpreter, computer use, image generation).	March 2025
Agents SDK	Open-source Python/Node library for orchestrating single- and multi-agent workflows (handoffs, guardrails, tracing). Successor to Swarm.	March 2025
AgentKit	Higher-level toolkit bundling Agent Builder (visual workflow canvas), ChatKit (embeddable chat UI), and Connector Registry (centralized data-source management).	October 2025

The Agent Platform page is OpenAI’s marketing umbrella for all of the above.

Google Agent Development Kit (ADK)

Open-source, modular framework optimized for Gemini but model-agnostic.
Supports single-agent and multi-agent topologies.
Deployment targets:
- Vertex AI Agent Engine — fully managed, auto-scaling.
- Cloud Run — containerized, BYO infrastructure.
- GKE — Kubernetes-based deployment.

Interoperability Protocol

MCP (Model Context Protocol)

Open standard originally created by Anthropic, now governed by The Linux Foundation and open to community contributions (protocol & SDKs, server registry).
Clients (Claude, ChatGPT, VS Code, JetBrains IDEs, Cursor, etc.) attach to MCP servers that expose tool schemas.
Rapidly becoming the de facto interoperability layer for agentic systems.
Growing registry of community and vendor servers (GitHub, Azure DevOps, Notion, Playwright, Slack, databases, etc.).
Key value: write your tools once, expose them to any MCP-compatible client — no per-client integration work.
All three frameworks above support MCP natively or via plugins.

Governance Layers

MuleSoft Agent Fabric (Salesforce)

Enterprise governance layer for agent fleets:
- Registry — catalog of available agents and tools.
- Broker — routes requests to the right agent.
- Policies — access control, rate limiting, data-loss prevention.
- Observability — centralized logging and tracing.
Supports MCP as a connectivity standard.
Designed for organizations running dozens to hundreds of agents at scale.

Multi-Agent Teams

A growing pattern is containerized agent teams — groups of domain-specialized agents that collaborate under a shared governance envelope:

AgentCatalog on Docker Hub is an early example: pre-built agent images for common tasks.
Teams can be composed dynamically (e.g., a “contract review” team with a clause-extraction agent, a risk-scoring agent, and a summarization agent).
Container orchestration (Kubernetes, Docker Compose) enables scaling, versioning, and rollback at the agent level.
Internal governance and access policies can be enforced per container.

Reference Architectures

#	Architecture	Key Components
1	Azure-first, workflow-heavy	Microsoft Agent Framework orchestrator → MCP server on Azure Container Apps → Azure AI services
2	OpenAI-first, builder-heavy	AgentKit / Agent Builder → Agents SDK → MCP server (any host)
3	GCP-first, ADK-centric	ADK agent on Vertex AI Agent Engine → MCP server on Cloud Run
4	Governed fleet	MuleSoft Agent Fabric broker → multiple MCP servers → policy enforcement layer

All four converge on MCP as the tool-connectivity standard. The choice is driven by existing cloud footprint, vendor relationships, and governance requirements.

From Zero to Production: An Implementation Plan

Each phase has a clear deliverable and exit criteria so you know when to move on (or loop back).

Phase 1 — Define Your Tool Surface

Goal: Decide what to expose before writing any code.

Audit your system’s existing APIs and workflows. Identify 3–5 high-value operations that agents would realistically call — e.g., searching documents, extracting entities, checking a case status, generating a summary.
For each operation, answer:
- What are the required vs. optional inputs? (Strictly type them.)
- What does the happy-path output look like? What about the error output?
- Is the operation read-only or does it have side-effects?
Write tool schemas (JSON Schema or equivalent) with:
- A clear, agent-readable description — this is what the LLM sees to decide whether to call the tool.
- A mode parameter ("concise" | "detailed") to control output verbosity.
- Cursor-based pagination (cursor + limit) for list endpoints.
- A truncated: true flag in responses so the agent knows to fetch more.
- Teaching errors — error messages that tell the agent how to fix the call, not just that it failed.

Deliverable: A schema document (OpenAPI or MCP tool definitions) reviewed by at least one person who did not write it.

Exit criteria: A teammate can read the schemas cold and correctly predict what each tool does, what inputs it needs, and what the output looks like.

Phase 2 — Build the MCP Server

Goal: Turn the schemas into a running server that any MCP client can connect to.

Implement each tool behind an MCP-compliant server (TypeScript or Python SDK).
Choose your transport based on use case:

Transport	When to Use
stdio	Local development, IDE integrations (VS Code, Cursor)
Streamable HTTP	Remote / cloud-hosted deployment, multi-tenant scenarios

Bake safety in from day one:
- Tools with side-effects must support a dry_run mode (returns what would happen) and a commit mode (executes the action).
- Destructive operations require a human-confirmation step before commit proceeds.
Validate interoperability with at least two MCP clients (e.g., Claude Desktop + VS Code Copilot). If both can discover and correctly call every tool, the server is ready.

Deliverable: A deployed (or locally runnable) MCP server with passing integration tests against two clients.

Exit criteria: Both clients can complete a realistic multi-step task end-to-end using only the exposed tools.

Phase 3 — Connect an Agent Framework

Goal: Prove the MCP server works with a real agent — pick one framework to start.

Choose the framework that matches your team’s stack:

If your stack is…	Start with…
Azure / .NET	Microsoft Agent Framework
OpenAI-heavy / Python	Agents SDK + Agent Builder
GCP / Gemini	Google ADK → Vertex AI Agent Engine

Build two things:

A deterministic workflow — a fixed sequence of tool calls (e.g., “search → extract → summarize”). This validates that the tools compose correctly.
A free-form agent — same tools, but the LLM decides the plan at runtime. This stress-tests your schemas: if the agent picks the wrong tool or passes bad inputs, your descriptions or error messages need work.

Optionally, repeat with a second framework to confirm the MCP server is truly framework-agnostic.

Deliverable: A working agent (workflow + free-form) that completes real tasks using the MCP server.

Exit criteria: The agent completes ≥ 80% of test tasks without human intervention.

Phase 4 — Evaluate and Iterate

Goal: Measure how well agents use your tools — and fix what’s broken.

Create 10–20 realistic tasks with expected ground-truth outputs (e.g., “Find all contracts expiring in Q2 and summarize the key obligations”).
Run each task through both the workflow and free-form agent. For every run, capture:

Metric	Why It Matters
Success rate	Did the agent reach the correct answer?
Tool-call count	Excess calls → schema is confusing
Token usage	Proxy for cost
Latency	End-to-end and per-tool
Error rate by category	Reveals systematic tool-design issues

Triage failures:
- Wrong tool selected → improve the tool description.
- Wrong parameters → tighten the schema, add enum constraints, improve error hints.
- Correct call, wrong interpretation of result → simplify the output format or add a summary field.
Re-run the eval suite after each fix. Track improvement over iterations.

Deliverable: An eval suite (automated, re-runnable) and a log of schema changes with before/after success rates.

Exit criteria: ≥ 90% success rate on the eval suite with both agent modes.

Phase 5 — Harden and Scale

Goal: Prepare for production traffic and organizational rollout.

Observability. Instrument the MCP server with distributed tracing (OpenTelemetry) and structured logging. Every tool call should be traceable from the client request through to the backend system.
Rate limiting and access control. Decide who (which agents, which users) can call which tools, and at what throughput.
Governance at scale. If you expect multiple MCP servers or agent teams, adopt a broker/fabric layer (e.g., MuleSoft Agent Fabric) for:
- Centralized policy enforcement.
- Audit logging (who called what, when, with what inputs).
- Fleet-level monitoring and kill-switches.
Documentation. Publish a tool catalog — human-readable descriptions, example calls, known limitations — so other teams can build agents against your MCP server without reverse-engineering it.

Deliverable: A production-ready MCP server with monitoring dashboards, access policies, and a published tool catalog.

Exit criteria: A team that was not involved in building the server can stand up a new agent against it using only the catalog and public schemas.