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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so safety is covered. The description usefully adds the data provenance (CT logs, i.e. publicly logged certs only) and an explicit per-call price, which the annotations do not convey. It stops short of noting edge cases like domains with no logged certs.

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?

One front-loaded sentence covering purpose, source, and returns, followed by a short cost note. Every clause carries information; nothing is redundant with the title or schema.

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?

No output schema exists, so the description compensates by listing the result fields (cert, issuer, expiry, subdomains), which is sufficient for an agent to know what comes back. Minor gap: no mention of behavior for domains lacking logged certificates or of result volume for subdomains.

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?

With a single parameter at 100% schema coverage including an example ('shopify.com'), the schema already does the work and the baseline applies. The description adds only that the domain is looked up via CT logs, not new syntax or format semantics for the parameter.

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 ('Check'), a specific resource ('a domain's TLS certificates'), and names the data source (Certificate Transparency logs). It enumerates the returned fields (current certificate, issuer, days until expiry, subdomains), which clearly separates it from siblings like dns_lookup, security_headers, or domain_whois.

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?

The scope implies when it applies (need cert/issuer/expiry/subdomain data), but the description never explicitly routes against alternatives such as dns_lookup, security_headers, or domain_report. Usage is inferable rather than stated.

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