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

Annotations cover the safety profile (readOnly, idempotent), but the description adds two genuinely non-obvious behaviors: no credentials are required, and a limit value of `0` means unlimited rather than zero. The latter is a critical interpretation rule that would otherwise cause misreading of results.

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 tight sentences: purpose first, then usage and the sibling comparison, then the one caveat that matters. No filler, and the most surprising fact (0 = unlimited) is placed last where it stands out.

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?

With an output schema present and zero parameters, the description need only cover purpose, routing, and result interpretation — all of which it does. Nothing an agent needs to call or correctly read this tool 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?

The tool takes zero parameters, so the baseline is 4; the schema is trivially complete. The description correctly focuses on output interpretation rather than inventing parameter guidance.

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 ('List') and resource ('self-serve plans a company can subscribe to'), and scopes it to self-serve rather than all plan types. An agent can distinguish this from sibling catalog tools like get_capabilities immediately.

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?

Explicitly says when to use it ('compare quotas against what the user actually needs') and routes to the complementary sibling: get_capabilities for the current license vs. this tool for each plan's limits. It also states the precondition (no credentials needed).

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