CDP Status

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

Annotations already cover the safe-read profile, but the description adds substantial behavior beyond them: the default port and env-var controls, the failure mode (ok false plus setup steps when nothing answers), the fact that other tools are unaffected, and that it re-probes on every call so relaunches are detected. That is exactly the extra context annotations cannot convey.

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

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

Five tight sentences, front-loaded with what is reported before moving to defaults, the Arc launch prerequisite, failure behavior, and probe freshness. Each sentence carries distinct, load-bearing information with no filler.

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

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

There is no output schema, yet the description compensates by describing the returned fields (port, browser, target count, security warning) and the failure shape (ok false with setup steps). For a zero-parameter diagnostic tool this is complete enough to call correctly without any structured return definition.

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

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

The tool takes zero parameters, which is the baseline-4 case. The description correctly describes configuration via environment variables rather than parameters, so there is nothing further for it to clarify on this dimension.

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

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

States a precise verb+resource: it reports whether the CDP engine is usable and enumerates exactly what it returns (port, answering browser, page target count, security warning). It also distinguishes itself from the rest of the toolset by noting that every non-CDP tool is unaffected, so an agent can tell it apart from siblings like arc_status or get_current_tab.

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

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

Explains the operating conditions well: on by default, probes 127.0.0.1:9222, ARC_MCP_CDP_PORT overrides, ARC_MCP_CDP=0 disables, and Arc only serves the port when launched with --remote-debugging-port. It never explicitly says when to call it versus an alternative (e.g., as a preflight before CDP-dependent tools), so guidance is clear but not fully prescriptive.

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