go-sdk/mcp/tool.go
Jonathan Amsterdam 6378df6f24
all: remove ServerRequest[T] for concrete T (#342)
Replace all occurrences of ServerRequest[*CallToolParams] and other
concrete instantiations with CallToolRequest and the like.

Make the XXXRequest types aliases, to preserve the convenience of
generics for the internal machinery (see shared.go, for example.)

I will expand the aliases in a followup PR.
2025-08-21 12:10:53 -04:00

64 lines
2.1 KiB
Go

// Copyright 2025 The Go MCP SDK Authors. All rights reserved.
// Use of this source code is governed by an MIT-style
// license that can be found in the LICENSE file.
package mcp
import (
"bytes"
"context"
"encoding/json"
"fmt"
"github.com/google/jsonschema-go/jsonschema"
)
// A ToolHandler handles a call to tools/call.
// [CallToolParams.Arguments] will contain a map[string]any that has been validated
// against the input schema.
type ToolHandler func(context.Context, *CallToolRequest) (*CallToolResult, error)
// A ToolHandlerFor handles a call to tools/call with typed arguments and results.
type ToolHandlerFor[In, Out any] func(context.Context, *CallToolRequest, In) (*CallToolResult, Out, error)
// A serverTool is a tool definition that is bound to a tool handler.
type serverTool struct {
tool *Tool
handler ToolHandler
}
// unmarshalSchema unmarshals data into v and validates the result according to
// the given resolved schema.
func unmarshalSchema(data json.RawMessage, resolved *jsonschema.Resolved, v any) error {
// TODO: use reflection to create the struct type to unmarshal into.
// Separate validation from assignment.
// Disallow unknown fields.
// Otherwise, if the tool was built with a struct, the client could send extra
// fields and json.Unmarshal would ignore them, so the schema would never get
// a chance to declare the extra args invalid.
dec := json.NewDecoder(bytes.NewReader(data))
dec.DisallowUnknownFields()
if err := dec.Decode(v); err != nil {
return fmt.Errorf("unmarshaling: %w", err)
}
// TODO: test with nil args.
if resolved != nil {
if err := resolved.ApplyDefaults(v); err != nil {
return fmt.Errorf("applying defaults from \n\t%s\nto\n\t%s:\n%w", schemaJSON(resolved.Schema()), data, err)
}
if err := resolved.Validate(v); err != nil {
return fmt.Errorf("validating\n\t%s\nagainst\n\t %s:\n %w", data, schemaJSON(resolved.Schema()), err)
}
}
return nil
}
// schemaJSON returns the JSON value for s as a string, or a string indicating an error.
func schemaJSON(s *jsonschema.Schema) string {
m, err := json.Marshal(s)
if err != nil {
return fmt.Sprintf("<!%s>", err)
}
return string(m)
}