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

No annotations are provided, so the description bears full responsibility. It discloses that page content is not stored, but it fails to mention that many parameters are discarded after validation (as noted in the schema descriptions) and that the tool appears to handle multiple data types (URLs, cities, JSON, file paths, timezones, etc.). The actual behavior is much broader than described, and there is no mention of errors, rate limits, or return structure beyond the three URL fields.

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 concise and front-loaded with the core action, but it is under-specified given the tool's complexity. Two sentences omit critical information about the other parameters and the tool's multi-purpose nature. It is not verbose, but it sacrifices completeness for brevity.

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 has 9 parameters, no output schema, and no annotations. The description only explains the URL behavior, leaving the purpose and expected behavior for all other parameters undocumented. An agent cannot know what the tool does with city, feed, json, path, zone, query, etc., nor what it returns for those inputs. This is a significant completeness gap.

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 each parameter already has a clear explanation. The description adds no semantic value for parameters; it only describes the URL-related output. Since the schema does the heavy lifting, a baseline of 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?

The description states a specific action for URLs (return host, scheme, HTTP status) and adds a distinguishing behavioral note ('Page content is not stored'). However, it only describes the URL use case while the schema exposes 9 parameters (city, feed, json, path, zone, query, etc.), each implying additional checks. The description does not convey the tool's broader scope, so an agent would under-estimate its capabilities and might misroute requests.

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?

No guidance is given on when to use this tool versus its siblings (normalize-url, fetch-status, web-fetch, etc.). The description does not mention alternatives, exclusions, or preferred contexts. The single hint ('Page content is not stored') implies a lightweight check, but it is not explicit about when to choose this over a content-fetching tool.

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