firefox_performance

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

Annotations already declare this a safe, idempotent read, so the description's real contribution is the data-quality disclosures: unauthorized origins are hidden, query/hash are stripped, and cross-origin timing may be restricted by Firefox. Those are non-obvious output characteristics an agent could otherwise misread as missing data. It stops short of describing the shape or ordering of results.

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?

Four short sentences, each carrying distinct information: capability, precondition, redaction behavior, and platform limitation. The capability is front-loaded and no sentence is 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?

With no output schema, the description should indicate what comes back (entry lists per timing category) and it does not; nor does it cover the three undocumented parameters. The behavioral caveats it does include are valuable, but for a three-parameter tool with zero schema documentation the definition is only partially complete.

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?

Schema description coverage is 0%, so the description carries the full burden for tabId, frameId and maxResults, yet none of them are mentioned. An agent gets no clue from prose that maxResults caps collection at 200 or that frameId scopes to a subframe, leaving all three parameters to be inferred from bare types.

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?

The description names a specific verb ('Read') and concrete resource set ('native Navigation, Paint and Resource Timing'), which unambiguously places it in the Performance Timing API domain and separates it from siblings like firefox_network and firefox_console. It does not explicitly contrast itself with those siblings, which keeps it just below the top mark.

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?

'Requires debug access' is a genuine prerequisite that tells the agent a precondition exists before calling. However, there is no guidance on when to prefer this over firefox_network or firefox_console for timing questions, and no statement about when the tool is not appropriate.

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