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

Annotations already declare readOnlyHint, destructiveHint=false and openWorldHint=false, so safety is covered; the description adds real behavioral context by scoping terms_url to usage terms only and flagging that plan, price and purchase details are absent. It doesn't describe the response shape, but an output schema exists so that burden is lower.

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?

Every sentence carries information, but the opening sentence chains six concepts with 'plus' into a single ~60-word clause, which hurts front-loading and scannability. A short lead ('Returns plan-wide limits and rules metadata') followed by the enumeration would read far better.

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?

The description covers scope, non-scope, the sibling alternative, and what terms_url contains; the return shape is documented by the output schema. It is complete enough to call correctly, though the enumeration of returned fields is tangled enough that an agent may need a second pass to map it.

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 and there is nothing for the description to disambiguate. The description correctly implies a parameterless global read.

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 names a specific verb (read) and enumerates the exact resources returned: weekly included Credit coverage, private Space usage rates, available features, terms_url, assistant availability, and request/response limits. It is clearly distinguishable from account_get_usage, which it names. The only drawback is that the first sentence is a dense run-on that takes effort to parse, but the content is precise.

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?

It explicitly routes the agent: a signed-in person's own coverage comes from account_get_usage, and pricing/purchase questions are out of scope and belong on the O++ website. Both the alternative tool and the when-not condition are stated, with an instruction on what to say instead.

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