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qckfx

Node.js Debugger MCP Server

by qckfx

pause_execution

Pause the debugged Node.js process to inspect code state during debugging sessions. This tool halts execution for analysis.

Instructions

Pause execution of the debugged process

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault

No arguments

Implementation Reference

  • The handler function for the 'pause_execution' tool. Checks if a debug session is active, then invokes Debugger.pause() via the Chrome DevTools Protocol (CDP) client to pause execution, returning appropriate success or error messages.
    private async pauseExecution() {
      if (!this.debugSession.connected || !this.debugSession.client) {
        return {
          content: [
            {
              type: "text",
              text: "No active debug session. Please attach debugger first.",
            },
          ],
          isError: true,
        };
      }
    
      try {
        const { Debugger } = this.debugSession.client;
        await Debugger.pause();
    
        return {
          content: [
            {
              type: "text",
              text: "Execution paused successfully",
            },
          ],
        };
      } catch (error) {
        return {
          content: [
            {
              type: "text",
              text: `Error pausing execution: ${error}`,
            },
          ],
          isError: true,
        };
      }
  • src/index.ts:218-225 (registration)
    Registration of the 'pause_execution' tool in the tools list returned by ListToolsRequestSchema handler. Includes name, description, and empty input schema (no parameters required).
    {
      name: "pause_execution",
      description: "Pause execution of the debugged process",
      inputSchema: {
        type: "object",
        properties: {},
      },
    },
  • Input schema definition for the 'pause_execution' tool, specifying an empty object (no input parameters required).
    inputSchema: {
      type: "object",
      properties: {},
    },
  • src/index.ts:262-263 (registration)
    Dispatch/registration case in the CallToolRequestSchema switch statement that routes calls to the pauseExecution handler.
    case "pause_execution":
      return await this.pauseExecution();
Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries full burden for behavioral disclosure. It states the action ('Pause execution') but lacks critical details: whether this requires specific permissions, if it's reversible (e.g., via a resume command), what happens to process state during pause, or error conditions (e.g., fails if no debugger attached). The description is minimal and doesn't compensate for missing annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, efficient sentence with no wasted words. It's front-loaded with the core action and target, making it immediately understandable. Every word earns its place by conveying essential purpose without redundancy or fluff.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the complexity of a debugger operation with no annotations and no output schema, the description is incomplete. It doesn't explain what 'pause' entails (e.g., halts threads, preserves state), what the expected outcome is (e.g., success confirmation, error if not debuggable), or how it interacts with sibling tools. For a mutation tool in a debugging context, more behavioral context is needed.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool has 0 parameters with 100% schema description coverage, so the schema fully documents the absence of inputs. The description doesn't need to add parameter semantics, and it correctly doesn't mention any parameters. A baseline of 4 is appropriate for zero-parameter tools when the schema coverage is complete.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the action ('Pause execution') and target ('debugged process'), providing a specific verb+resource combination. It distinguishes from siblings like 'kill_process' (terminates) and 'step_debug' (single-step execution) by focusing on suspension. However, it doesn't explicitly differentiate from all siblings (e.g., 'set_breakpoint' also affects execution flow).

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides no guidance on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., requires an active debug session), exclusions (e.g., cannot pause if already paused), or when to choose siblings like 'step_debug' for finer control or 'kill_process' for termination instead of suspension.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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