Method executeTool

apps/sim/lib/mcp/service.ts:249–301

* Execute a tool on a specific server with retry logic for session errors. * Retries once on session-related errors (400, 404, session ID issues).

(
    userId: string,
    serverId: string,
    toolCall: McpToolCall,
    workspaceId: string,
    extraHeaders?: Record<string, string>
  )

   * Retries once on session-related errors (400, 404, session ID issues).
   */
  async executeTool(
    userId: string,
    serverId: string,
    toolCall: McpToolCall,
    workspaceId: string,
    extraHeaders?: Record<string, string>
  ): Promise<McpToolResult> {
    const requestId = generateRequestId()
    const maxRetries = 2

    for (let attempt = 0; attempt < maxRetries; attempt++) {
      try {
        logger.info(
          `[${requestId}] Executing MCP tool ${toolCall.name} on server ${serverId} for user ${userId}${attempt > 0 ? ` (attempt ${attempt + 1})` : ''}`
        )

        const config = await this.getServerConfig(serverId, workspaceId)
        if (!config) {
          throw new Error(`Server ${serverId} not found or not accessible`)
        }

        const { config: resolvedConfig, resolvedIP } = await this.resolveConfigEnvVars(
          config,
          userId,
          workspaceId
        )
        if (extraHeaders && Object.keys(extraHeaders).length > 0) {
          resolvedConfig.headers = { ...resolvedConfig.headers, ...extraHeaders }
        }
        const client = await this.createClient(resolvedConfig, resolvedIP, userId)

        try {
          const result = await client.callTool(toolCall)
          logger.info(`[${requestId}] Successfully executed tool ${toolCall.name}`)
          return result
        } finally {
          await client.disconnect()
        }
      } catch (error) {
        if (this.isSessionError(error) && attempt < maxRetries - 1) {
          logger.warn(
            `[${requestId}] Session error executing tool ${toolCall.name}, retrying (attempt ${attempt + 1}):`,
            error
          )
          await sleep(100)
          continue
        }
        throw error
      }
    }

    throw new Error(`Failed to execute tool ${toolCall.name} after ${maxRetries} attempts`)
  }

  /** MCP spec: server returns 404 for unknown session id, 400 for malformed header. */
  private isSessionError(error: unknown): boolean {