Use ergonomic provider initialization pattern

[jlowin]

The FastMCP constructor already accepts a providers kwarg, but examples and convenience methods were using a less ergonomic three-step pattern. This updates them to use the cleaner approach.

Before:

provider = OpenAPIProvider(openapi_spec=spec, client=client)
mcp = FastMCP("API Server")
mcp.add_provider(provider)

After:

provider = OpenAPIProvider(openapi_spec=spec, client=client)
mcp = FastMCP("API Server", providers=[provider])

Changes apply to:

• SQLite provider example
• OpenAPI provider documentation
• FastMCP.from_openapi() and FastMCP.from_fastapi() convenience methods

[coderabbitai]

Walkthrough

This pull request refactors provider setup across multiple files to consolidate the two-step initialization process into a single-step approach. Previously, code would instantiate a FastMCP server and then invoke add_provider() separately. The changes update the FastMCP constructor to accept an optional providers parameter, allowing providers to be passed directly during instantiation. All call sites—including examples in examples/providers/sqlite/server.py, the OpenAPI server module, and the factory methods from_openapi() and from_fastapi()—are updated to use this new constructor-based pattern. The runtime behavior of provider attachment remains unchanged; only the initialization style is modified.

Possibly related PRs

• feat: Provider abstraction for dynamic MCP components #2622: Introduces the providers parameter and add_provider() method to the FastMCP constructor, which this PR leverages throughout the codebase.
• Refactor FastMCPProxy into ProxyProvider #2669: Demonstrates equivalence between the add_provider() pattern and direct provider passing via constructor, directly supporting the refactoring performed in this PR.

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'Use ergonomic provider initialization pattern' clearly and specifically summarizes the main change: adopting a cleaner, more ergonomic approach to provider initialization in FastMCP.
Description check	✅ Passed	The description provides a clear explanation of the change with before/after code examples and lists all affected areas, though it lacks the structured checklist items from the template.
Docstring Coverage	✅ Passed	Docstring coverage is 80.00% which is sufficient. The required threshold is 80.00%.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch ergonomic-provider-init

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📥 Commits

Reviewing files that changed from the base of the PR and between 96c7a74 and ab63256.

📒 Files selected for processing (4)

• examples/providers/sqlite/server.py
• src/fastmcp/server/openapi/server.py
• src/fastmcp/server/providers/openapi/__init__.py
• src/fastmcp/server/server.py

🧰 Additional context used

📓 Path-based instructions (2)

**/*.py

📄 CodeRabbit inference engine (AGENTS.md)

**/*.py: Use Python ≥ 3.10 with full type annotations
Never use bare except - be specific with exception types

Files:

• src/fastmcp/server/server.py
• src/fastmcp/server/providers/openapi/__init__.py
• src/fastmcp/server/openapi/server.py
• examples/providers/sqlite/server.py

src/fastmcp/**/__init__.py

📄 CodeRabbit inference engine (AGENTS.md)

Core types that define a module's purpose should be exported (e.g., Middleware from fastmcp.server.middleware), while specialized features can live in submodules

Files:

• src/fastmcp/server/providers/openapi/__init__.py

🧠 Learnings (1)

📚 Learning: 2025-11-03T17:36:13.363Z

Learnt from: jlowin
Repo: jlowin/fastmcp PR: 2355
File: docs/clients/client.mdx:226-246
Timestamp: 2025-11-03T17:36:13.363Z
Learning: In FastMCP documentation, prefer showing the happy path in onboarding examples without over-explaining edge cases or adding defensive checks, as this reduces cognitive burden for new users learning the API.

Applied to files:

• src/fastmcp/server/openapi/server.py

🧬 Code graph analysis (1)

examples/providers/sqlite/server.py (1)

src/fastmcp/server/server.py (1)

• FastMCP (157-2949)

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (4)

• GitHub Check: Run tests: Python 3.10 on windows-latest
• GitHub Check: Run tests: Python 3.13 on ubuntu-latest
• GitHub Check: Run tests: Python 3.10 on ubuntu-latest
• GitHub Check: Run tests with lowest-direct dependencies

🔇 Additional comments (7)

examples/providers/sqlite/server.py (1)

104-105: LGTM!

The ergonomic provider initialization pattern is correctly applied. The provider is instantiated and passed directly to the FastMCP constructor via the providers kwarg, which aligns with the constructor's providers: Sequence[Provider] | None parameter.

src/fastmcp/server/openapi/server.py (3)

11-11: LGTM!

The module docstring example correctly demonstrates the new ergonomic provider initialization pattern.

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54-57: LGTM!

The "New approach" example in the class docstring correctly demonstrates the recommended pattern with providers=[provider].

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90-96: LGTM!

The deprecation warning message correctly guides users to the new ergonomic pattern. The internal add_provider() call on line 117 is intentionally preserved for backwards compatibility in this deprecated wrapper class.

src/fastmcp/server/server.py (2)

2779-2791: LGTM!

The from_openapi() factory method now correctly uses the single-step provider initialization pattern by passing providers=[provider] directly to the constructor. This aligns with the PR objectives and is cleaner than the previous two-step approach.

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2825-2848: LGTM!

The from_fastapi() factory method correctly mirrors the from_openapi() change, passing providers=[provider] directly to the constructor for consistent ergonomic initialization.

src/fastmcp/server/providers/openapi/__init__.py (1)

6-14: LGTM!

The module docstring example correctly demonstrates the new ergonomic provider initialization pattern, consistent with the changes across the codebase.

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