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congzhou09

chrome-dev-mcp

by congzhou09
OverviewSchemaRelated ServersScoreDiscussions
TypeScript
Local

set_breakpoint

Idempotent

Pause JavaScript execution in Chrome by setting a breakpoint with an exact URL or regex and line number to debug specific code.

Instructions

Set a breakpoint by URL (exact or regex) + line number.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
urlNoExact script URL. Provide this or urlRegex; if both, urlRegex takes precedence.
urlRegexNoURL regex pattern. Provide this or url; if both, urlRegex takes precedence.
conditionNoJS expression; breakpoint triggers only when truthy
lineNumberYesLine number (1-indexed)
columnNumberNoColumn number, 1-indexed (optional)

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
breakpointIdYes
resolvedLocationsYesMay be empty if the script is not loaded yet; the breakpoint will bind automatically when Chrome parses the script

Schema Changelog

Changes observed during successful MCP inspections. Dates show when Glama detected each change.

  1. Changed11 schema fields changedv1.3.0
    • changedInput schema / properties / columnNumber / description
      Previous value: -"Column number (optional)"New value: +"Column number, 1-indexed (optional)"
    • addedInput schema / properties / columnNumber / maximum
      Added value: +9007199254740991
    • addedInput schema / properties / columnNumber / minimum
      Added value: +1
    • changedInput schema / properties / columnNumber / type
      Previous value: -"number"New value: +"integer"
    • addedInput schema / properties / lineNumber / maximum
      Added value: +9007199254740991
    • addedInput schema / properties / lineNumber / minimum
      Added value: +1
    • changedInput schema / properties / lineNumber / type
      Previous value: -"number"New value: +"integer"
    • changedInput schema / properties / url / description
      Previous value: -"Exact script URL, or omit to use urlRegex"New value: +"Exact script URL. Provide this or urlRegex; if both, urlRegex takes precedence."
    • changedInput schema / properties / urlRegex / description
      Previous value: -"URL regex pattern (alternative to exact url)"New value: +"URL regex pattern. Provide this or url; if both, urlRegex takes precedence."
    • changedInput schema / required
      Previous value: -[
-  "url",
-  "lineNumber"
-]New value: +[
+  "lineNumber"
+]
    • changedOutput schema / (root)
      Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": false,
+  "properties": {
+    "breakpointId": {
+      "type": "string"
+    },
+    "resolvedLocations": {
+      "description": "May be empty if the script is not loaded yet; the breakpoint will bind automatically when Chrome parses the script",
+      "items": {
+        "additionalProperties": false,
+        "properties": {
+          "columnNumber": {
+            "type": "number"
+          },
+          "lineNumber": {
+            "type": "number"
+          },
+          "scriptId": {
+            "type": "string"
+          }
+        },
+        "required": [
+          "scriptId",
+          "lineNumber"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    }
+  },
+  "required": [
+    "breakpointId",
+    "resolvedLocations"
+  ],
+  "type": "object"
+}
  2. First observedv1.1.0

TDQS

A4/5.0
Behavior3/5

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

Annotations include idempotentHint=true, which already communicates that repeated calls are safe. The description adds no extra behavioral context such as whether existing breakpoints are overwritten, persistence, or side effects. With annotations present, the bar is lower, but the description still adds minimal value beyond the schema.

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, front-loaded sentence with no filler. It communicates the essential purpose and selection criteria in under 15 words.

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?

With a fully descriptive schema and an output schema present, the description only needs to summarize the core action, which it does. It does not mention optional parameters like condition or columnNumber, but their absence is acceptable since the schema covers them. The description is sufficient for an agent to select and invoke the tool.

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 baseline is 3. The description mentions URL (exact or regex) and line number, but those are already fully described in the schema. It does not add additional meaning about condition, columnNumber, or precedence rules, which are also covered by 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?

The description clearly states the action ('Set') and resource ('breakpoint'), and specifies the key inputs (URL exact or regex + line number). It distinguishes this from sibling tools like remove_breakpoint and list_breakpoints by focusing on creation.

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?

The description provides clear context for when to use this tool (to create a breakpoint) by naming the selection method (URL exact/regex) and line number. It does not explicitly mention alternatives or when not to use it, but the context is unambiguous for a simple tool. No exclusions are needed given the sibling list.

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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