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MCP Debugger

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TypeScript
Hybrid

pause_execution

Pauses a running program for debugging. Waits briefly; if it can't stop within ~5s, returns success with pending:true, and fails with an actionable error if no debuggable target exists.

Instructions

Pause a running program. Waits briefly for the stop; if the program cannot stop within ~5s (e.g. blocked in native code, or an idle server waiting for input), returns success with pending:true and the session reports "paused" the next time the program runs code. Fails with an actionable error if the session has no debuggable target to pause (e.g. a js attach whose target session was never adopted or has ended)

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
threadIdNoThread ID to pause. If omitted or 0, pauses all threads.
sessionIdYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv0.20.0
    • addedInput schema / properties / threadId
      Added value: +{
+  "description": "Thread ID to pause. If omitted or 0, pauses all threads.",
+  "type": "number"
+}
  2. First observed

TDQS

A3.8/5.0
Behavior5/5

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

With no annotations, the description carries the full burden and does so richly: it discloses the ~5s grace period, the pending:true success fallback for programs blocked in native code or idle servers, the deferred 'paused' state, and an actionable failure mode when no debuggable target exists. This is exactly the behavioral context an agent needs.

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?

Three tightly packed sentences: the action first, then the async/pending semantics, then the failure mode. Every clause earns its place with no redundancy.

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

Completeness4/5

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

For a pause tool with no annotations and no output schema, the description covers runtime behavior and failure modes thoroughly, including the pending:true return. The one notable gap is that sessionId is undocumented and the description doesn't explain how to identify a valid debuggable session.

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

Parameters2/5

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

Schema coverage is 50%: threadId is well documented in the schema ('omitted or 0 pauses all threads'), but sessionId has no description anywhere. The description adds no parameter-level meaning to compensate for that gap, so it fails to help the agent understand the required sessionId.

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 opens with a specific verb+resource: 'Pause a running program.' This cleanly separates it from continue_execution and the step_* siblings by name implication. It doesn't explicitly name which sibling to prefer, but the purpose is unambiguous.

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

Usage Guidelines3/5

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

The description implies usage (pause a running program), and it describes the error condition when there is no debuggable target. However, it never states when to choose pause over step_over or continue_execution, nor any explicit exclusions. Usage is only implied.

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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