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

Annotations already mark this as read-only and non-destructive, and the description goes beyond that by disclosing that the endpoint is 'exempt from every metering stage' and consumes no hourly call, concurrency slot, or credit. It also warns that ceilings are per-plan and change without a release, adding important behavioral context not available from annotations or schema.

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?

The description is front-loaded with the core purpose, then efficiently expands with a bullet-like list of answered questions, a critical no-cost guarantee, and explicit when-to-use guidance. Every sentence earns its place; there is no filler or repetition of schema details.

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 tool has only two optional parameters, an output schema, and rich annotations, so the description's coverage of purpose, cost implications, plan-dependence, and usage timing is complete. An agent can confidently decide when and why to call check_limits without needing additional context.

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 description coverage is 100%, so both api_key and response_format are already fully documented. The description adds general context about per-plan ceilings, but it does not materially extend the semantic meaning of either parameter beyond what the schema already states.

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 opening sentence states a specific verb and resource: 'Report what this caller may do right now.' It then enumerates concrete metrics (searches left, plan reach, limit, concurrency, wait time), and explicitly contrasts itself with the `news` tool descriptions, which cannot answer these questions. This makes the tool's purpose unambiguous and separates it from its most likely confusing sibling.

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?

The description gives clear guidance: use it before planning batch calls and after plan-limit or rate-limit errors, rather than guessing the ceiling. It does not explicitly compare with alternative siblings like check_coverage or check_health, but the intended triggers are specific and actionable.

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