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

The description discloses key traits beyond the annotations: timeouts and connection failures are returned as 'down with the reason, not as an error,' redirects are followed, and each call costs $0.01 with 25 free and failed calls free. These details clarify error semantics, cost, and the idempotentHint=false behavior (repeats are charged), which the annotations alone do not 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?

The purpose and output list are front-loaded in the first sentence, and the usage cases follow. The pricing and billing sentences are relevant but make the description slightly dense; it remains efficient overall.

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 fully covers the return contract: status, up/down, response time, final URL, content type, server header, page size, and optional text match. It also explains failure semantics and billing, so an agent has everything needed to call and interpret the tool.

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 coverage is 100% and both parameters ('url', 'contains') are already documented in the input schema. The description restates the optional text check and gives an example URL, but adds no new syntax or constraint information beyond what the schema provides, so baseline 3 is appropriate.

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 opens with a precise verb and resource: 'Check whether a website is up right now,' then enumerates the exact outputs (HTTP status, up/down, response time, final URL, content type, server header, page size). It clearly distinguishes itself from sibling url_meta and url_redirects by framing the call as a live uptime probe with a specific diagnostic payload.

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?

It lists concrete use cases: 'uptime monitoring, health checks before calling an API, or to confirm a deploy,' which gives an agent clear selection context. It does not explicitly state when not to use it or name a sibling as the alternative, so it falls short of the top score.

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