file-search-on: Skill for Claude Code

Add MCP Tool

The MCP server in internal/mcpserver/server.go exposes tools to MCP clients (Claude Desktop, IDE plugins) via the official Go SDK at github.com/modelcontextprotocol/[email protected]. Adding a tool is four small things in one file plus a test in another. The schema is generated from struct tags — you don't write JSON schema by hand.

Prefer extending the existing search tool's input over forking a new tool when the new capability is "search but with one more filter / option". MCP clients see fewer entry points and the model picks the right one more reliably.

The four parts of a tool

1. Input/output structs with json and jsonschema tags. The SDK derives the JSON schema from these.
2. Handler function matching ToolHandlerFor[In, Out]:

   func(ctx context.Context, req *mcp.CallToolRequest, in In) (*mcp.CallToolResult, Out, error)
   

3. Registration via mcp.AddTool(s, &mcp.Tool{...}, handler) inside New(version).
4. Test in server_test.go driving the new tool through mcp.NewInMemoryTransports().

Quick start

Adding a hypothetical read_attributes tool that returns the full attribute set for a single file:

1. Add the structs in internal/mcpserver/server.go, near the existing SearchInput / SearchOutput:

   type ReadAttributesInput struct {
       Path string `json:"path" jsonschema:"Path to a single file. Required."`
   }
   
   type ReadAttributesOutput struct {
       Path        string         `json:"path"`
       ContentType string         `json:"content_type"`
       Size        int64          `json:"size"`
       Attributes  map[string]any `json:"attributes"`
   }
   

2. Write the handler, near the existing searchHandler:

   func readAttributesHandler(ctx context.Context, _ *mcp.CallToolRequest, in ReadAttributesInput) (*mcp.CallToolResult, ReadAttributesOutput, error) {
       attrs, err := celexpr.BuildAttributes(in.Path, content.DefaultRegistry())
       if err != nil {
           return nil, ReadAttributesOutput{}, fmt.Errorf("build attributes: %w", err)
       }
       return nil, ReadAttributesOutput{
           Path:        attrs.Path,
           ContentType: attrs.ContentType,
           Size:        attrs.Size,
           Attributes:  attrs.Extra,
       }, nil
   }