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

Adds real cost/idempotency context beyond the readOnly and idempotent annotations: no credit spent, no brief started, and errors are actionable with a concrete URL_REDIRECTS_ELSEWHERE code carrying a suggested_url. This is exactly the kind of information an agent needs to safely retry or self-correct.

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?

Four short sentences, each carrying distinct information: purpose, input, return values, cost/error behaviour. Front-loaded with the decision-relevant clause ('before spending anything') and no 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?

Covers purpose, accepted input shape, return contents (normalised domain, company name or null, credits), cost side-effects and error remediation. With an output schema present, the description gives just enough without duplicating it.

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 the schema already states 'domain such as acme.com, or a URL on it. Not a LinkedIn or directory page.' The description's 'Pass the domain (acme.com) or any URL on it' restates that with no additional format or normalisation syntax, so it adds little beyond the schema.

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 — validate that a company's website is usable for a brief before spending credits — which is clearly distinct from get_account, get_brief, list_briefs and request_brief. It does not name any sibling, so the differentiation is implied by the 'before spending anything' framing rather than stated.

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?

'before spending anything' plus 'Free: no credit is spent and no brief is started' establishes clear pre-conditions for calling this instead of the paid path. It stops short of naming request_brief as the tool to use afterwards, leaving the alternative implicit.

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