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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety and network reach are covered. The description adds genuine behavioral context beyond that: redirects are not followed, and HEAD vs GET trade-off is noted, which matters for interpreting the returned status. It stops short of timeout, rate-limit, or error-handling behavior.

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?

A single front-loaded sentence that leads with the action, then the method options and constraint, then the return payload. No filler or repetition.

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?

For a simple two-parameter read-only tool with no output schema, the description enumerates exactly what comes back (status code, status text, response time, headers) and discloses the redirect and method behavior, so an agent has everything needed to call and interpret it.

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 description coverage is 100%, including the private/loopback/metadata rejection rule and the method semantics, so the schema does the heavy lifting. The description restates the GET/HEAD choice and redirect behavior but adds no format or syntax detail beyond the schema, matching the baseline for fully documented parameters.

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 ('Request a URL ... return its HTTP status code, status text, response time in ms and response headers'), naming method options and the redirects-not-followed constraint. This implicitly separates it from siblings like trace_redirects and generate_status_url, so an agent can route correctly without opening the 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?

Usage is implied by the tool's narrow scope (check whether a URL is reachable and what it returns). However, no sibling is named and no condition is given for choosing this over check_cors, scan_security_headers, or trace_redirects, leaving the agent to infer the boundary.

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