fix: resolve MCP manifest validation errors for use_cases and examples fields

- Increase use_cases maxItems constraint from 3 to 5 to match actual usage
- Add field_validator for string array length validation (max 200 chars per item)
- Implement smart truncation at word boundaries with ellipsis
- Fix imports to include ValidationInfo from pydantic
- Reduce start_pre_ingestion examples from 4 to 3 to comply with constraints
- Handle various input types (string/list) for MCP client compatibility

Fixes validation error: "['Understanding API evolution...'] is too long"

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: Peter

src/docsrs_mcp/app.py

@@ -652,8 +652,7 @@ async def get_mcp_manifest(request: Request):
                 ),
                 examples=[
                     "start_pre_ingestion()",
-                    "start_pre_ingestion(force=true)",
-                    "start_pre_ingestion(concurrency=5)",
+                    "start_pre_ingestion(force=true, concurrency=5)",
                     "start_pre_ingestion(count=200, concurrency=5)",
                 ],
                 use_cases=[

src/docsrs_mcp/models.py

@@ -10,7 +10,14 @@
 from enum import Enum
 from typing import Any, Literal
 
-from pydantic import BaseModel, ConfigDict, Field, field_validator, model_validator
+from pydantic import (
+    BaseModel,
+    ConfigDict,
+    Field,
+    ValidationInfo,
+    field_validator,
+    model_validator,
+)
 
 from . import config as app_config
 from .validation import validate_crate_name, validate_rust_path, validate_version_string
@@ -56,11 +63,53 @@ class MCPTool(BaseModel):
     use_cases: list[str] | None = Field(
         None,
         description="Common use cases for this tool",
-        json_schema_extra={"maxItems": 3},
+        json_schema_extra={"maxItems": 5},  # Increased to match actual usage
     )
 
     model_config = ConfigDict(extra="forbid")
 
+    @field_validator("use_cases", "examples", mode="before")
+    @classmethod
+    def validate_string_arrays(
+        cls, v: Any, info: ValidationInfo
+    ) -> list[str] | None:
+        """Validate string arrays with length constraints."""
+        if v is None:
+            return None
+
+        # Handle string input (split by newlines or commas)
+        if isinstance(v, str):
+            v = [
+                item.strip() for item in v.replace("\n", ",").split(",") if item.strip()
+            ]
+
+        # Ensure list type
+        if not isinstance(v, list):
+            v = [v]
+
+        # Validate constraints
+        field_name = info.field_name
+        max_items = 5 if field_name == "use_cases" else 3
+        max_length = 200  # Reasonable limit for individual strings
+
+        if len(v) > max_items:
+            raise ValueError(
+                f"{field_name} cannot exceed {max_items} items (got {len(v)})"
+            )
+
+        # Validate and truncate individual strings
+        validated = []
+        for i, item in enumerate(v):
+            item_str = str(item).strip()
+            if len(item_str) > max_length:
+                # Truncate at word boundary with ellipsis
+                truncated = item_str[: max_length - 3].rsplit(" ", 1)[0] + "..."
+                validated.append(truncated)
+            else:
+                validated.append(item_str)
+
+        return validated if validated else None
+
 
 class MCPResource(BaseModel):
     """