Skip to main content
Glama
Sign In
MCP Debugger

MCP Debugger

by debugmcp
OverviewSchemaSourceRelated ServersDiscussionsAdmin
TypeScript
Hybrid

pause_execution

Pauses a running program to inspect its state; if it cannot stop immediately, returns pending status so you can wait for the next stop.

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 (call wait_for_stop to block until then). An observed stop answers with stopReason, the first visible frame as location (with its source context), and note when the stop was reported on a thread with no program frame — a sibling thread in program code is shown instead, or, when none has one, the note says no program frame is active. 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

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

A4.1/5.0
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: it discloses the ~5s timeout, the pending:true partial-success state, the reasons a stop may not be observed (native code, idle server), the async semantics of the session reporting "paused" later, the returned fields (stopReason, location, note), the thread-frame fallback logic, and the actionable-error case. This is unusually complete behavioral disclosure.

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

Conciseness3/5

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

The purpose is front-loaded in the first clause, but the remaining text is a dense run-on with stacked parentheticals (the thread-frame explanation is nearly unparseable on one read). The information earns its place, but the packaging makes it harder to extract than necessary.

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?

There is no output schema, so the description rightly explains the return shape (stopReason, location, note, pending) and the error path — a real strength. The only gap is the undocumented sessionId, which is likely conventional across all sibling debugger tools.

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 only 50% — threadId is documented but sessionId has no description anywhere. The description adds no parameter-level meaning at all: it never mentions sessionId, and it does not restate the important "omit threadId to pause all threads" behavior, so the agent gets nothing beyond the schema.

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

Purpose5/5

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

States a specific verb and resource ("Pause a running program") and immediately differentiates itself from the sibling wait_for_stop by explaining which case calls for which. An agent can distinguish it from continue_execution, step_over, and wait_for_stop without opening a schema.

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

Usage Guidelines4/5

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

It gives a clear trigger (a running program), a fallback path ("call wait_for_stop to block until then"), and a failure condition (no debuggable target). It does not explicitly exclude anything, but the routing to the alternative covers the main ambiguity.

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

Deploy Server

Other Tools