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

With no annotations, the description carries the full burden and does most of it: it declares 'Read-only' itself, discloses that it fetches the URL both as an AI agent and as a browser (i.e. it performs live external requests, not a cached lookup), and enumerates the possible verdicts. It stops short of stating rate limits, auth needs, or whether the probes are logged server-side.

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?

Front-loads the purpose ('Before an agent browses or fetches a site, check if it will get in') and closes with the two operational sentences. The middle clause is a dense enumeration, but each listed check and each verdict value earns its place since nothing else documents them.

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 and no annotations, the description compensates well by naming all five verdict values and the 'plus advice' return, and it covers scope and timing. It is short only on operational details like rate limits, caching, or what the advice contains — minor gaps for a read-only probe 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?

One parameter at 100% schema description coverage, so the schema already documents the url field and its example. The description adds no syntax, format, or constraint detail beyond the schema (e.g. whether bare domains are normalized, redirect depth), so the baseline 3 applies.

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 specific verb and resource ('check if it will get in' before browsing/fetching a site) and enumerates exactly what the tool inspects: bot challenges, robots.txt rules for named crawlers, and agent doors like llms.txt/MCP/OpenAPI. The singular 'the URL' implicitly scopes it to one page, distinguishing it from the batch sibling check_many without needing to name it.

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?

Gives explicit positive and negative guidance: 'Use it before an automated web task, not for pages you already fetched successfully.' That is a clear when-to-use plus an exclusion, but it never routes the agent to the sibling alternatives (check_many for batches, find_agent_alternative for fallbacks), which the top tier requires.

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