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

With no annotations provided, the description carries the full disclosure burden. The only behavioral disclosure is 'Page content is not stored,' which is genuinely useful. But the description conceals that the tool actually branches across nine different input behaviors (city→weather, json→validation, zone→timezone, query→length check, etc.), which is a major transparency failure — the agent does not know what the tool really does for non-URL inputs.

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?

Two short sentences, front-loaded with the primary action and a useful privacy note second. No wasted words. It loses a point only because its brevity is partly a symptom of under-specification — it is short because it omits the other eight behaviors entirely.

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 9-parameter, 0-required, no-output-schema tool with no annotations, the description must explain what each param does and what is returned. It covers only the URL case, leaving the other eight behaviors and the return format for non-URL inputs entirely unspecified. The tool is far too complex for such a thin description; the agent cannot correctly invoke it for city, json, zone, query, or feed inputs.

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 schema already documents all 9 parameters with useful notes ('discarded after the shape check', 'no disk access', etc.). The description adds zero parameter-level value beyond the schema; it only mentions the URL parameter indirectly. It does not need to compensate since the schema carries the load, hence a 3.

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 clear verb+resource for the URL case ('Return host, scheme, and HTTP status for a URL'), which is specific and distinguishes from the URL-related siblings. However, the schema reveals 9 heterogeneous parameters (git refs, weather cities, RSS feeds, JSON validation, file paths, timezones, search queries) that the description entirely omits, so the stated purpose covers only a fraction of the tool's actual behavior and is misleading about its scope.

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 many overlapping siblings (normalize-url, fetch-status, web-fetch, browser-url-ok, playwright-url-ok, validate-json, timezone, utc-time, weather-hint, iana-zones, search-query-len). No exclusions, no conditions, no alternative routing. Given the dense sibling landscape, an agent cannot determine which tool handles a given input.

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