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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false, covering the safety profile. The description adds behavioral value by disclosing that it checks reachability, latency, redirects, and content type—behavior not required by the schema. It does not mention that a fee applies, though the title signals '$0.001 USDC', which is a cost behavior not disclosed in the description body.

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?

One sentence, front-loaded with the verb and resource, and contains only the essential facts: what is checked (reachability, status, latency, redirects, content type) and when to use it ('before using it'). No filler, no redundancy with the schema. The title adds cost information separately, which is acceptable.

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?

The tool is simple (2 params, 1 required), has full schema coverage, and an output schema exists, so the description doesn't need to explain return values. The only notable gap is cost transparency: the title carries the '$0.001 USDC' fee, but the description itself omits any mention of the cost or any rate-limit implications. For a single-URL check with these annotations, this is nearly 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 coverage is 100%, so the baseline is 3. The description adds minimal parameter-level meaning beyond the schema, but the 'before using it' framing implies the tool is a validation step and that the result matters for downstream decisions. It does not describe the format of expectedStatus matching beyond what the schema already states, so it only slightly exceeds the baseline.

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?

Description uses a specific verb ('Check') with a clear resource ('one public URL') and enumerates concrete outputs (reachability, HTTP status, latency, redirects, content type). It also distinguishes itself from siblings like batch_check_urls by explicitly saying 'one public URL', which differentiates it from the batch variant.

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?

The phrase 'before using it' implies the intended use case is pre-flight validation of a URL. It does not explicitly name alternatives like batch_check_urls or verify_web_evidence, nor does it state when NOT to use it. However, the contextual phrasing and the sibling batch tool provide sufficient implied guidance for an agent to pick this for single-URL checks.

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