fix(mcp_server): validate tool arguments before dispatch, return JSON-RPC errors on bad params

[christauff]

Problem

handle_request() dispatches tool calls directly with **tool_args before any validation:

result = TOOLS[tool_name]["handler"](**tool_args)

If a caller passes wrong types or omits required parameters, raw Python exceptions leak into the JSON-RPC error response. Callers receive unstructured tracebacks instead of standards-compliant error objects. This also means any MCP client can probe internal implementation details through exception messages.

Fix

Add _validate_tool_args() — a lightweight validator that checks required parameters are present and that declared types match the tool's existing input_schema definitions:

def _validate_tool_args(tool_name: str, tool_args: dict, req_id) -> dict:
    schema = TOOLS[tool_name]["input_schema"]
    # check required params present
    # check declared types match
    # return JSON-RPC -32602 error dict on violation, or None if valid

Wire it into the tools/call handler before the dispatch call:

validation_error = _validate_tool_args(tool_name, tool_args, req_id)
if validation_error:
    return validation_error
result = TOOLS[tool_name]["handler"](**tool_args)

On violation, callers receive a proper {"code": -32602, "message": "Missing required parameter: 'query'"} error. The handler is never invoked. No logic changes to existing tools.

Test plan

• Call search tool without query parameter → JSON-RPC error -32602 Missing required parameter: 'query'
• Call kg_add tool with confidence as string instead of number → JSON-RPC error -32602 Parameter 'confidence' must be number, got str
• All 19 tools with valid parameters → behavior unchanged, handlers invoked normally
• Malformed JSON body → existing error handling unchanged (validation only runs after successful parse)

🤖 Generated with Claude Code

[bensig]

Solid work on the validation + tests. CI lint is failing though — can you run ruff check . and ruff format . and push a fix?

[web3guru888]

🔧 Review of #91 — fix(mcp_server): validate tool arguments before dispatch, return JSON-RPC errors on bad params

Scope: +123/−0 · 2 file(s) · touches core

• ⚠️ mempalace/mcp_server.py (modified: +40/−0)
• tests/test_mcp_server.py (added: +83/−0)

Technical Analysis

• 🔌 MCP server dispatch changes — verify JSON-RPC compliance and backward compatibility

Issues

• ⚠️ Touches mempalace/mcp_server.py — Core MCP server — maintainer guards this closely

Suggestions

• Magic number(s) 32602 — consider extracting to named constant(s)

Strengths

• ✅ Includes test coverage

🟡 Needs attention — touches guarded files and has items to address.

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_{🏛️ Reviewed by MemPalace-AGI · Autonomous research system with perfect memory · Showcase: Truth Palace of Atlantis}

[bensig]

Closing — this is superseded by recently merged PRs to develop. Thank you for the contribution!