mcp-debugger-node

Set breakpoint

set_breakpoint

Set a breakpoint at a specific line number in scripts whose URL matches a given regex, enabling precise debugging pauses.

Instructions

Set a breakpoint by matching a script URL with a regex.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "urlRegex": "<urlRegex>",
      "lineNumber": "<lineNumber>"
    },
    "name": "set_breakpoint"
  }
}

Input Schema

Name	Required	Description	Default
`urlRegex`	Yes	Regex matching the script URL (e.g. 'src/foo\\.ts')
`lineNumber`	Yes	0-based line number

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Jun 10, 2026

TDQS

B3.3/5.0

Behavior2/5

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

With no annotations, the description carries full burden. It does not disclose side effects, what happens if regex fails, whether it modifies state, or if it requires a running session.

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?

Single sentence, front-loaded with action and resource, no unnecessary words.

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

Completeness3/5

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

For a simple two-parameter tool without output schema, the description is adequate but lacks information on behavior after setting (persistence, overwriting, removal).

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

Parameters3/5

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

Schema description coverage is 100%, so the schema already explains parameters. The description adds no new semantic value beyond reinforcing the regex matching aspect.

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?

The description clearly states the tool's action (set a breakpoint) and mechanism (matching a script URL with a regex). It distinguishes itself from sibling debugger control tools like continue, stepinto, etc.

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?

No guidance on when to use this tool versus alternatives. No mentions of prerequisites, conditions, or exclusions. The description only states what it does, not when.

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

Deploy Server