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browser_start_capture

Capture network, console, navigation, and WebSocket events from a browser session to debug web applications.

Instructions

Capture network, console, navigation, and WebSocket events. Request and response bodies default off; when requested, text/JSON bodies are size-bounded and held only in memory.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
session_idYes
duration_msNo
max_body_bytesNo
capture_request_bodiesNo
capture_response_bodiesNo

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

B3.3/5.0
Behavior3/5

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

With no annotations, the description carries the burden and does add real behavioral context: bodies default off, text/JSON bodies are size-bounded, and data is held only in memory (a meaningful non-persistence signal). It omits whether the call blocks, what happens when duration_ms is 0, and any auth/permission requirements.

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?

Two short sentences with zero padding; the capture scope is front-loaded and the body-handling caveat follows. Every clause earns its place.

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 5-parameter tool with no annotations and no output schema, the description covers body behavior well but leaves key operational details (duration_ms semantics, session prerequisite, what the capture returns/where to read it) unstated. Adequate but with clear gaps.

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 0%, so the description must compensate; it clarifies capture_request_bodies/capture_response_bodies defaulting off and that max_body_bytes bounds text/JSON body size. However, session_id and duration_ms (including the 0 default) are left entirely unexplained, so coverage is partial.

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?

States a specific verb (capture) and enumerates the captured resources (network, console, navigation, WebSocket events), so the agent knows exactly what this tool produces. It is distinguishable from retrieval siblings like browser_get_events or browser_list_network_requests, though it does not explicitly name them.

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 never says when to call this versus alternatives, nor does it note the obvious pairing with browser_stop_capture or the prerequisite of an open session. Usage is only implied by the verb 'capture'.

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