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

With no annotations, the description carries the full burden. It discloses that this is a GET meta endpoint reporting usage for the current key, which implies a safe read-only operation. It doesn't explicitly state 'has no side effects' or describe error behavior, but for a simple usage endpoint the core behavior is well covered.

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 no filler. The first sentence front-loads the endpoint and returned data; the second gives concrete use cases. 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 parameterless tool with no output schema, the description is complete: it names the resource, enumerates the returned fields, and specifies when to invoke it. An agent has enough to select, call, and interpret the result.

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?

There are zero parameters and schema coverage is 100%, so there is nothing for the description to add about inputs. The baseline for a parameterless tool applies; the description appropriately focuses on output and usage context instead.

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 states exactly what the tool returns: the current key's tier, monthly cap, requests used and remaining, and reset time. It also names the endpoint (GET /v1/_meta/usage), making the purpose unmistakable and clearly distinguishing it from the legislative data tools listed as siblings.

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 explicit trigger conditions: 'Call this when a request is rate-limited (HTTP 429) or the user asks about their plan.' This is direct, actionable guidance and no alternative sibling tool is relevant, so no exclusions are needed.

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