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

With no annotations, the description must disclose behavior fully. It mentions the HEAD method and 'status only' output, which is useful, but it does not explain that many parameters are 'discarded after the shape check' or that the tool may validate non-URL inputs. This omission is significant for a tool with 9 parameters and no other behavioral context.

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 description is a single, concise sentence that front-loads the primary action and output. It is efficient and free of fluff. The brevity is a strength, but it sacrifices necessary detail about the tool's broader behavior.

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 9 parameters, no output schema, and no annotations, the description is insufficient for an agent to understand the tool's full behavior. It does not explain why parameters like 'city' or 'zone' exist, what 'shape check' means, or how the tool handles these alongside URL fetching. The description is incomplete and potentially misleading for agent selection and invocation.

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%, so the baseline is 3. The description itself adds no parameter-level detail; the schema already explains each field. However, the schema's phrasing like 'discarded after the shape check' is ambiguous, and the description does not clarify how parameters relate to the stated URL-status purpose, so it adds little beyond the schema.

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 states a specific action (HEAD a public URL) and output (status only), making the core purpose clear. However, the 9-parameter schema suggests the tool actually validates multiple input shapes (ref, city, json, etc.), which the description does not mention. This narrow scope is potentially misleading about the tool's full capability, so clarity is only partial.

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?

There is no guidance on when to use this tool versus siblings like browser-url-ok, web-fetch, or normalize-url. The description does not mention alternatives, exclusions, or the appropriate context for a HEAD status check versus a full fetch. An agent has to guess based on the name and description alone.

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