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

With no annotations, the description carries full behavioral burden. It does disclose the upstream data source (crt.sh) and that results are deduplicated, which is real value, but it omits rate limits, failure modes, and the fundamental coverage limitation of certificate transparency data.

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?

Three compact sentences, front-loaded with the core action and data source, followed by the return shape and the use case. Every sentence contributes something, though the use-case sentence is the weakest.

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 two-parameter tool with no output schema, the description does reasonably well by stating the return value (a deduplicated subdomain list). However, the undocumented 'limit' parameter and the absence of any coverage caveat leave meaningful gaps for correct invocation and interpretation.

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 only 50%: the 'domain' parameter is documented in-schema as an apex domain with no scheme or subdomain, but 'limit' has no description anywhere. The description adds nothing about either parameter — notably it never explains that 'limit' caps the subdomain list (default 100, max 500).

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 opens with a specific verb and resource ("Discover subdomains for a domain") and names the mechanism (Certificate Transparency logs via crt.sh). No sibling tool in the list performs subdomain enumeration, so an agent can select this without ambiguity.

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?

"Useful for security audits and asset inventory" hints at context but gives no explicit when-to-use vs when-not guidance, no prerequisites, and no caveat that CT logs only surface subdomains with issued certificates (so internal or never-certificated hosts will be missed).

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