googleapis/mcp-toolbox · error

%s is not a valid http method

Error message

%s is not a valid http method

What it means

After successfully unmarshalling the method string, it is uppercased and checked against the set of valid HTTP methods (GET, POST, PUT, DELETE, etc.). This error means the configured method string is not one of the supported HTTP verbs.

Source

Thrown at internal/tools/http_method.go:45

func isValidHTTPMethod(method string) bool {

	switch method {
	case http.MethodGet, http.MethodPost, http.MethodPut, http.MethodDelete,
		http.MethodPatch, http.MethodHead, http.MethodOptions, http.MethodTrace,
		http.MethodConnect:
		return true
	}
	return false
}

func (i *HTTPMethod) UnmarshalYAML(ctx context.Context, unmarshal func(interface{}) error) error {
	var httpMethod string
	if err := unmarshal(&httpMethod); err != nil {
		return fmt.Errorf(`error unmarshalling HTTP method: %s`, err)
	}
	httpMethod = strings.ToUpper(httpMethod)
	if !isValidHTTPMethod(httpMethod) {
		return fmt.Errorf(`%s is not a valid http method`, httpMethod)
	}
	*i = HTTPMethod(httpMethod)
	return nil
}

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Replace the method value with a standard HTTP verb: GET, POST, PUT, DELETE, PATCH, or HEAD as supported by isValidHTTPMethod
2. Fix the typo in the config (e.g. gtet -> get)
3. Check the library version's supported method list and upgrade if a needed verb is missing

Example fix

// before
method: fetch
// after
method: GET

var valid = map[string]bool{"GET":true,"POST":true,"PUT":true,"DELETE":true,"PATCH":true,"HEAD":true}
m := strings.ToUpper(cfg.Method)
if !valid[m] {
    return fmt.Errorf("%s is not a valid http method", m)
}

if err := yaml.Unmarshal(data, &cfg); err != nil {
    if strings.HasSuffix(strings.TrimSpace(err.Error()), "is not a valid http method") {
        // correct the method verb in tools.yaml
    }
    return err
}

When it happens

Trigger: A tools.yaml http tool declares method: fetch, method: patch (if unsupported), method: getall, or a typo like method: gtet; the string parses fine as YAML but fails isValidHTTPMethod after uppercasing.

Common situations: Typos in hand-edited configs; invented verbs ('UPSERT', 'READ'); casing confusion (handled by ToUpper, so this is genuinely an invalid verb, not a case issue); older configs written for a fork supporting extra verbs.

Related errors

• error parsing argument: %w
• invalid role %q: must be 'user' or 'assistant'
• unable to parse Timeout string as time.Duration: %s
• failed to parse BaseUrl %v
• invalid allowedIpRanges: %w

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/e408765c9f5c271f. Report an issue: GitHub.