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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, open-world), so the description's job is to add nuance, and it does: 'one ordinary page load plus public DNS' discloses the non-intrusive method and bounds side effects. It further discloses the A–F grading and that each issue ships with a fix, though it says nothing about duration, rate limits, or what happens to unreachable URLs.

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?

Front-loaded with the action and scope, then the graded signals, then a one-line disqualifier. The long signal enumeration is dense but each item carries information for the calling agent; nothing is repeated filler.

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?

With no output schema, the description still tells the agent what comes back (A–F grades plus a fix per issue) and what inputs are inspected (page load plus public DNS). It is complete enough to call correctly; only timing and failure behavior are unstated.

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?

The single parameter is fully documented in the schema (100% coverage) including accepted input forms ('example.com or https://example.com/pricing'). The description only adds the 'one public URL' constraint, which is marginal beyond the structured data, 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?

States a specific verb and resource ('Passive security check of one public URL') and enumerates the exact signals graded (HTTPS, HSTS, CSP, SPF, DMARC, DNSSEC, etc.). The scope limits ('one public URL', 'passive', 'Not a vulnerability scan') separate it from a bulk crawler or a vulnerability scanner without needing the sibling schemas.

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 rather than prescribed: 'one public URL' hints at single-target use versus bulk_check or full_site_crawl, and 'Not a vulnerability scan' rules out a class of expectation. There is no explicit when-to-use routing to alternatives such as seo_check or ai_visibility_check.

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