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mcp: unexport ToolFor #402

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Sep 3, 2025
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mcp: unexport ToolFor #402

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42 changes: 16 additions & 26 deletions mcp/server.go
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Original file line number Diff line number Diff line change
Expand Up @@ -154,10 +154,18 @@ func (s *Server) RemovePrompts(names ...string) {
// If present, the output schema must also have type "object".
//
// When the handler is invoked as part of a CallTool request, req.Params.Arguments
// will be a json.RawMessage. Unmarshaling the arguments and validating them against the
// input schema are the handler author's responsibility.
// will be a json.RawMessage.
//
// Most users should use the top-level function [AddTool].
// Unmarshaling the arguments and validating them against the input schema are the
// caller's responsibility.
//
// Validating the result against the output schema, if any, is the caller's responsibility.
//
// Setting the result's Content, StructuredContent and IsError fields are the caller's
// responsibility.
//
// Most users should use the top-level function [AddTool], which handles all these
// responsibilities.
func (s *Server) AddTool(t *Tool, h ToolHandler) {
if t.InputSchema == nil {
// This prevents the tool author from forgetting to write a schema where
Expand All @@ -181,26 +189,6 @@ func (s *Server) AddTool(t *Tool, h ToolHandler) {
func() bool { s.tools.add(st); return true })
}

// ToolFor returns a shallow copy of t and a [ToolHandler] that wraps h.
//
// If the tool's input schema is nil, it is set to the schema inferred from the In
// type parameter, using [jsonschema.For]. The In type parameter must be a map
// or a struct, so that its inferred JSON Schema has type "object".
//
// For tools that don't return structured output, Out should be 'any'.
// Otherwise, if the tool's output schema is nil the output schema is set to
// the schema inferred from Out, which must be a map or a struct.
//
// Most users will call [AddTool]. Use [ToolFor] if you wish to modify the
// tool's schemas or wrap the ToolHandler before calling [Server.AddTool].
func ToolFor[In, Out any](t *Tool, h ToolHandlerFor[In, Out]) (*Tool, ToolHandler) {
tt, hh, err := toolForErr(t, h)
if err != nil {
panic(fmt.Sprintf("ToolFor: tool %q: %v", t.Name, err))
}
return tt, hh
}

// TODO(v0.3.0): test
func toolForErr[In, Out any](t *Tool, h ToolHandlerFor[In, Out]) (*Tool, ToolHandler, error) {
tt := *t
Expand Down Expand Up @@ -335,10 +323,12 @@ func setSchema[T any](sfield **jsonschema.Schema, rfield **jsonschema.Resolved)
// For tools that don't return structured output, Out should be 'any'.
// Otherwise, if the tool's output schema is nil the output schema is set to
// the schema inferred from Out, which must be a map or a struct.
//
// It is a convenience for s.AddTool(ToolFor(t, h)).
func AddTool[In, Out any](s *Server, t *Tool, h ToolHandlerFor[In, Out]) {
s.AddTool(ToolFor(t, h))
tt, hh, err := toolForErr(t, h)
if err != nil {
panic(fmt.Sprintf("AddTool: tool %q: %v", t.Name, err))
}
s.AddTool(tt, hh)
}

// RemoveTools removes the tools with the given names.
Expand Down