Function checkRequest

mcp/shared.go:186–206

checkRequest checks the given request against the provided method info, to ensure it is a valid MCP request. If valid, the relevant method info is returned. Otherwise, a non-nil error is returned describing why the request is invalid. This is extracted from request handling so that it can be calle

(req *jsonrpc.Request, infos map[string]methodInfo)

// This is extracted from request handling so that it can be called in the
// transport layer to preemptively reject bad requests.
func checkRequest(req *jsonrpc.Request, infos map[string]methodInfo) (methodInfo, error) {
	info, ok := infos[req.Method]
	if !ok {
		return methodInfo{}, fmt.Errorf("%w: %q unsupported", jsonrpc2.ErrNotHandled, req.Method)
	}
	if info.flags&notification != 0 && req.IsCall() {
		return methodInfo{}, fmt.Errorf("%w: unexpected id for %q", jsonrpc2.ErrInvalidRequest, req.Method)
	}
	if info.flags&notification == 0 && !req.IsCall() {
		return methodInfo{}, fmt.Errorf("%w: missing id for %q", jsonrpc2.ErrInvalidRequest, req.Method)
	}
	// missingParamsOK is checked here to catch the common case where "params" is
	// missing entirely.
	//
	// However, it's checked again after unmarshalling to catch the rare but
	// possible case where "params" is JSON null (see https://go.dev/issue/33835).
	if info.flags&missingParamsOK == 0 && len(req.Params) == 0 {
		return methodInfo{}, fmt.Errorf("%w: missing required \"params\"", jsonrpc2.ErrInvalidRequest)
	}
	return info, nil
}

// methodInfo is information about sending and receiving a method.
type methodInfo struct {