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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false, openWorldHint=true), and the description adds genuinely useful behavior: JS is not executed during the fetch, the run takes about a minute, and if it exceeds ~25 seconds it returns a check_id for later retrieval. Rate limits or auth requirements are not mentioned.

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?

Three sentences, front-loaded with purpose and then behavior; each sentence carries information. The return-value sentence partly duplicates the output schema, which is mild waste but not harmful.

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?

Given an output schema exists and annotations carry the safety profile, the description supplies the key remaining context: the async check_id workflow and the ~1 minute runtime. It lacks sibling routing and prerequisites, but is otherwise sufficient to invoke correctly.

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?

Only one parameter with 100% schema description coverage, so the schema already documents the url field fully. The description adds only the 'one public page' constraint and no syntax or format detail beyond the schema, so the 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?

States a specific verb and resource: 'Runs the xfix search check on one public page', and enumerates the concrete checks (JS-less fetch, robots.txt for 9 crawlers, mobile speed, text/headings/title). Clear what it does, but it never names or differentiates from siblings like check_page_readability or check_ai_crawler_access.

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?

Usage is implied by 'on one public page' and the async fallback, but there is no explicit when-to-use vs alternatives guidance and no when-not conditions. The agent must infer that this is the broad visibility check versus the narrower sibling checks.

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