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

Annotations already cover the read-only and open-world profile, and the description adds real behavioral context beyond that: anonymous rate limiting per IP, refusal of private and reserved addresses, and the meaning of the `partial=true` flag. The main gap is that it never states the sample count or how many samples are taken by default, which materially affects what 'rate-limited' means in practice.

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 tight sentences, front-loaded with what is measured and returned, then constraints. Every clause carries a distinct fact and none restates the title or the schema.

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?

An output schema exists, so return values need not be exhaustively described, yet the description still summarizes them usefully. For a one-parameter, read-only measurement tool, an agent has everything it needs to decide to call it and to interpret the result.

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?

There is a single parameter with 100% schema description coverage, so the baseline is 3. The description adds contextual meaning to the sampling behavior ('over several samples') but gives no information about the `url` argument itself beyond what the schema already documents.

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?

Specific verb (measures) plus resource (URL response time) with the measurement unit and returned fields stated explicitly. It also carves out its scope against the sibling set with 'Measures the HTTP response only: no browser runs', which separates it from ping_test and website_status without the agent opening either schema.

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?

Clear context and explicit exclusions: no JavaScript, no assets, no Core Web Vitals, and 'a snapshot, not a trend' tells the agent not to use it for monitoring over time. It stops short of naming a specific alternative sibling (e.g. ping_test for ICMP or a browser-based tool for CWV), so routing is inferred rather than spelled out.

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