HTTP headers

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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds meaningful context beyond them: direct network contact, redirect following, and the fact that results are not cached (so repeat calls re-hit the site). What it omits – rate limits or timeout behavior – is minor.

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 core action and return summary, then the caveats (direct contact, alternative tool, no caching). The header enumeration is long but each item is genuinely part of the output contract, so it earns its place; only mild tightening is possible.

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 carries the full burden of describing returns and does so concretely (status, redirect chain, final URL, headers, missing-security-header list). For a single-parameter read tool it leaves nothing essential unspecified.

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?

Only one parameter and schema coverage is 100%, so the schema already documents the URL format and bare-domain handling. The description adds nothing about the parameter, which is the expected baseline when the schema does the heavy lifting.

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 ('One GET request to a URL') with explicit scope (follows redirects) and enumerates the return surface, including a security-header checklist. An agent can distinguish it from siblings like tls_certificate without opening any schema.

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?

Explicitly routes the certificate use case to tls_certificate and clarifies that this tool contacts the site directly like a browser visit, which sets expectations for when it applies. It stops short of a full when/when-not rule, but the context is clear and actionable.

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