API usage

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

Annotations already convey read-only, idempotent, and non-destructive behavior. The description adds context that the tool reports on the API key itself, not an address, and explains its diagnostic value for quota failures. This exceeds the annotation baseline without contradicting it.

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 short sentences: the first delivers the core function, the second gives usage triggers, the third clarifies the boundary versus siblings. No filler words, with the most important information front-loaded.

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, read-only tool with an output schema and comprehensive annotations, the description covers purpose, scope, and usage conditions. Nothing an agent needs to invoke 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?

The tool has zero parameters, so the schema already covers everything. The description confirms this with 'Takes no arguments,' adding no unnecessary detail while reinforcing the schema's emptiness.

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 a specific verb ('Report') and resource ('calling API key's plan, rate limits and monthly allowance'), immediately distinguishing it from all sibling token-focused tools. The explicit exclusion of token functionality ('Not for anything about a token') further eliminates ambiguity.

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: 'Use it when a call fails on quota, or when the user asks what their DeFade plan includes.' It also states what it is not for ('Not for anything about a token') and clarifies the contrast with every other tool in the suite.

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