Python: fix(claude): send the declared JSON schema of tools to Claude

[Md. Shalah Uddin (shanto462)]

Motivation & Context

ClaudeAgent built each tool's input schema from func_tool.input_model.model_json_schema() and used {} when input_model was None. A FunctionTool declared with a JSON schema dict keeps input_model = None, so these tools reached Claude with no parameters. That includes @tool(schema={...}), Agent.as_tool() and the vector store tools. Claude then called them without the arguments they need. The conversion also rebuilt every schema from only type, properties, required and $defs, so other top-level keywords such as additionalProperties: false were dropped and Claude saw a looser contract than the tool declares.

Description & Review Guide

• What are the major changes? _function_tool_to_sdk_mcp_tool passes the tool's full JSON schema from func_tool.parameters() (the Pydantic model's JSON schema or the dict schema the tool was declared with) to the Claude Agent SDK, so top-level keywords such as additionalProperties, title and $defs are kept. type is always "object" and a missing or null properties becomes {}, because the SDK only uses a dict with a string type and a properties key as a JSON schema; any other dict is read as a {name: python type} map. Tests check that a dict-schema tool keeps its full schema (additionalProperties: false, title, $defs with a $ref) and that its handler still runs, that a Pydantic extra="forbid" model keeps additionalProperties: false, and that a schema without an object type or properties (or with properties: null) gets both while the tool's own schema stays unchanged.
• What is the impact of these changes? Dict-schema tools reach Claude with their declared parameters and constraints. Pydantic-model and signature-based tools also keep their top-level keywords now, for example title, and additionalProperties: false for a model with extra="forbid". The SDK validates arguments against this schema, so such a tool now rejects extra arguments, as it declares. A schema without required no longer gets an empty required list, which means the same.
• What do you want reviewers to focus on? Passing the schema through whole matches the Anthropic, Bedrock and GitHub Copilot integrations, which already send tool.parameters() as is. Only type and a missing properties are set, so the SDK does not misread the schema. One thing to know: a declared schema with top-level anyOf, oneOf or allOf now sends those keywords to Claude too, as the Anthropic chat client already does; before, they were dropped together with the parameters.

Related Issue

Fixes #9301

No other open PR covers this issue.

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Contribution Checklist

• The code builds clean without any errors or warnings
• All unit tests pass, and I have added new tests where possible
• The PR follows the Contribution Guidelines
• This PR links to an agreed issue with no competing open PR, or the Related Issue section documents a trivial-change or repository-automation exception.
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[Copilot]

🟢 Approval recommended

The focused fix uses the established schema API and includes appropriate regression coverage.

0 open findings

What changed in this PR

Fixes Claude tool conversion so dict-based JSON schemas retain their declared parameters.

Changes:

• Uses FunctionTool.parameters() as the schema source.
• Adds regression coverage for schema preservation and handler execution.

File	Description
python/​packages/​claude/​agent_framework_claude/​_agent.py	Sources schemas from the unified tool API.
python/​packages/​claude/​tests/​test_claude_agent.py	Tests dict-schema conversion and invocation.

🧠 Review effort: Balanced

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[Eduard van Valkenburg (eavanvalkenburg)]

Md. Shalah Uddin (@shanto462) The PR now reads the declared tool schema, but _agent.py rebuilds it with only type, properties, required, and $defs, so valid top-level constraints such as additionalProperties: false are still dropped before reaching the Claude Agent SDK. That makes Claude see a looser contract than the tool declares. Please pass the full schema through (or preserve every top-level keyword) and add a regression proving a schema-declared tool retains additionalProperties: false.

[Md. Shalah Uddin (shanto462)]

Eduard van Valkenburg (@eavanvalkenburg) Fixed in dfd9f80: the full schema from parameters() is now passed through, with only type: "object" and a missing properties set so the SDK reads it as a JSON schema, and new regressions check that a declared schema and a Pydantic extra="forbid" model keep additionalProperties: false.