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

Annotations already establish read-only, idempotent, open-world, and non-destructive behavior. The description adds context beyond that by specifying what it returns (metadata, not content) and explicitly denying a safety guarantee, which is a valuable behavioral clarification. No contradiction with annotations.

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 three concise sentences, each adding distinct value: the purpose and start-here directive, the return-type clarification and free nature, and a concrete example. It is front-loaded with the critical usage instruction and avoids any fluff.

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 preflight tool with rich annotations and fully documented parameters, the description covers usage, return contents, limitations, and an example. It could specify the exact output structure, but the listed metadata fields are sufficient for an agent to know what to expect. The lack of an output schema does not hinder correct 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 coverage is 100% and both parameters have detailed descriptions (e.g., 'Public HTTP(S) document URL. No credentials, private networks...' and maxChars limits). The description only provides an example usage, which adds marginal value. The schema carries the semantic weight, so the 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 clearly states the tool's purpose: 'check a public URL before buying cited extraction' and enumerates the returned metadata (fetchability, provenance, hashes, deterministic injection indicators). It explicitly distinguishes itself from the paid sibling by saying 'No payment or purchase' and 'not page text or a safety guarantee.' This leaves no ambiguity about what the tool does.

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?

'Start here' and 'before buying cited extraction' provide explicit guidance on when to use this tool. The warning that it does not return page text or a safety guarantee tells the agent what not to expect, and the free/no-payment note sets it apart from the sibling tool. This is strong, actionable usage guidance.

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