chore: sync from fn-registry agent

tool_show.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+
+	"github.com/mark3labs/mcp-go/mcp"
+)
+
+type showArgs struct {
+	ID string `json:"id"`
+}
+
+func showTool() mcp.Tool {
+	return mcp.NewTool("fn_show",
+		mcp.WithDescription("Return a markdown card for the given function or type ID. Includes frontmatter-style header, description, signature, code block, examples and notes. Use after fn_search to fetch details."),
+		mcp.WithString("id",
+			mcp.Required(),
+			mcp.Description("Registry ID (e.g. filter_slice_go_core, Result_go_core)."),
+		),
+	)
+}
+
+func (d *deps) handleShow(ctx context.Context, _ mcp.CallToolRequest, args showArgs) (*mcp.CallToolResult, error) {
+	if args.ID == "" {
+		return mcp.NewToolResultError("id is required"), nil
+	}
+	if f, err := d.db.GetFunction(args.ID); err == nil {
+		md := truncate(renderFunctionMarkdown(f), 50_000)
+		out := map[string]any{"id": f.ID, "entity": "function", "markdown": md}
+		b, _ := json.MarshalIndent(out, "", "  ")
+		return mcp.NewToolResultText(string(b)), nil
+	}
+	if t, err := d.db.GetType(args.ID); err == nil {
+		md := truncate(renderTypeMarkdown(t), 50_000)
+		out := map[string]any{"id": t.ID, "entity": "type", "markdown": md}
+		b, _ := json.MarshalIndent(out, "", "  ")
+		return mcp.NewToolResultText(string(b)), nil
+	}
+	return mcp.NewToolResultError("id not found: " + args.ID), nil
+}