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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world. The description adds non-obvious behavior beyond that: it returns suggestions when the label is unavailable, and the current subdomain is reported as available. Return shape and rate limits are not covered, but this is meaningful added context.

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, zero waste, with the core operation front-loaded and the availability caveat following. Every clause earns its place.

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 read-only check with no output schema, the description covers what it does, the suggestion fallback, and one important edge case. It could say a bit more about what the response contains, but nothing needed to call it correctly is missing.

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 both parameters (project UUID, subdomain label) are already documented in the schema. The description reinforces the 'this project' scoping but adds no syntax or format detail beyond what the schema provides, so the baseline of 3 applies.

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') and resource ('subdomain label') with scope ('for this project') and secondary behavior ('get suggestions'). It is clearly distinguishable from siblings like update_project_subdomain or lookup_domain, though it never names them.

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?

Usage is implied: check availability before setting a subdomain. The note that the project's own subdomain reads as available is a helpful usage caveat, but there are no explicit when/when-not rules or named alternatives (e.g. lookup_domain vs update_project_subdomain).

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