mastra-ai/mastra · error · Error

Failed to fetch resource templates from server ${this.client

Error message

Failed to fetch resource templates from server ${this.client.name}: ${e instanceof Error ? e.stack || e.message : String(e)}

What it means

InternalMastraMCPClient's resources.templates() wraps any failure from the MCP resources/templates/list request in this Error after logging it. It signals the resource-template listing round-trip with the named server did not succeed, with the underlying error preserved in the message/stack.

Source

Thrown at packages/mcp/src/client/actions/resource.ts:111

      if (response && response.resourceTemplates && Array.isArray(response.resourceTemplates)) {
        return response.resourceTemplates;
      } else {
        this.logger.warn('Resource templates response did not have expected structure', {
          server: this.client.name,
          response,
        });
        return [];
      }
    } catch (e: any) {
      // MCP Server might not support resources, so we return an empty array
      if (e.code === ProtocolErrorCode.MethodNotFound) {
        return [];
      }
      this.logger.error('Error getting resource templates from server', {
        server: this.client.name,
        error: e instanceof Error ? e.message : String(e),
      });
      throw new Error(
        `Failed to fetch resource templates from server ${this.client.name}: ${e instanceof Error ? e.stack || e.message : String(e)}`,
      );
    }
  }

  /**
   * Reads the content of a specific resource from the MCP server.
   *
   * @param uri - URI of the resource to read (e.g., 'file://path/to/file.txt')
   * @returns Promise resolving to the resource content
   * @throws {Error} If reading the resource fails or resource not found
   *
   * @example
   * ```typescript
   * const result = await client.resources.read('file://data/config.json');
   * console.log(result.contents[0].text); // Resource text content
   * ```
   */

View on GitHub (pinned to 75dd419e61)

Solutions

1. Check the inner error for the true cause
2. Confirm the server advertises resource template support; fall back to resources.list() if not
3. Reconnect the client if the transport dropped
4. Retry with backoff on transient failures

Example fix

// before
const templates = await client.resources.templates();
// after
try {
  var templates = await client.resources.templates();
} catch (e) {
  templates = await client.resources.list(); // fallback
}

if (!client.isConnected()) await client.connect();

let templates;
try {
  templates = await client.resources.templates();
} catch (e) {
  logger.warn('templates/list failed, falling back to resources.list()', e instanceof Error ? e.message : e);
  templates = await client.resources.list();
}

When it happens

Trigger: Calling client.resources.templates() when resources/templates/list throws — server unreachable, transport closed, JSON-RPC error, or the server does not support resource templates.

Common situations: Older MCP servers that predate the resource-templates capability; flaky network to a remote server; server restarted between connect() and the templates call.

Related errors

• Failed to fetch resources from server ${this.client.name}: $
• Failed to fetch prompts from server ${this.client.name}: ${e
• Could not connect to server with any available HTTP transpor
• MCP_CLIENT_READ_RESOURCE_FAILED
• MCP_CLIENT_SUBSCRIBE_RESOURCE_FAILED

AI-assisted analysis of mastra-ai/mastra@75dd419e61 (2026-08-30). Data as JSON: /api/errors/eca7ba2fd7a32d44. Report an issue: GitHub.