mcp/internal/tools/get_symbol.go

package tools

import (
	"context"
	"strings"

	"code.nochebuena.dev/einherjar/mcp/internal/index"
	"github.com/modelcontextprotocol/go-sdk/mcp"
)

type getSymbolInput struct {
	Module     string `json:"module" jsonschema:"the module name, e.g. core"`
	Name       string `json:"name" jsonschema:"the symbol name; for methods use Type.Method"`
	SubPackage string `json:"subPackage,omitempty" jsonschema:"narrow to a specific sub-package, e.g. launcher"`
}

type getSymbolOutput struct {
	Matches []index.Symbol `json:"matches"`
}

func registerGetSymbol(s *mcp.Server, idx *index.Index) {
	mcp.AddTool(s, &mcp.Tool{
		Name:        "get_symbol",
		Description: "Fetch full signature, doc comment, and source location for one symbol. For a struct type the result includes its fields (name, type, struct tag, doc); for an interface type it includes its method set. Returns every match across sub-packages — use the subPackage filter when ambiguous.",
	}, func(ctx context.Context, req *mcp.CallToolRequest, args getSymbolInput) (*mcp.CallToolResult, getSymbolOutput, error) {
		m := idx.FindModule(args.Module)
		if m == nil {
			return errorResult("module not found: " + args.Module), getSymbolOutput{}, nil
		}
		out := getSymbolOutput{Matches: []index.Symbol{}}
		for _, sym := range m.Symbols {
			if !strings.EqualFold(sym.Name, args.Name) {
				continue
			}
			if args.SubPackage != "" && sym.SubPackage != args.SubPackage {
				continue
			}
			out.Matches = append(out.Matches, sym)
		}
		return jsonText(out), out, nil
	})
}