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

Annotations already declare a non-read-only, non-destructive, non-idempotent create, so the safety profile is covered. The description adds the genuinely useful two-step fact that guardrails live in a library and must be attached separately, but says nothing about name collisions, duplicate creation, or whether `enabled` defaults on.

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?

Two tight sentences with the core action front-loaded and the workflow hint second. No filler, no restatement of the title.

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 4-parameter mutation tool with 25% schema coverage and no output schema, the description covers the concept but omits defaults (`enabled`), uniqueness behavior for `name`, and what is returned. Adequate but with clear holes an agent would have to guess around.

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 schema coverage at only 25%, the description must compensate, and it partially does by mapping 'named' and 'writing rules' to the name and rules parameters. It never addresses `enabled` or why `site` is required on a library-scoped resource, leaving gaps the schema cannot fill.

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 ('Adds a named set of writing rules to the library') and clarifies what a guardrail actually is, which the bare name does not convey. An agent can distinguish this from list_guardrails, update_guardrail, and delete_guardrail without opening 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?

Names update_site_guardrails as the follow-up step, which is real workflow routing, so the agent knows creating alone does not apply the guardrail anywhere. It stops short of explicit when-not guidance (e.g. use update_guardrail to modify an existing one).

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