api_budget

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds real behavioral context beyond that: the monthly cap, ledger persistence surviving restarts, and the fact that cached repeats are free and uncounted — quota and accounting semantics the annotations cannot express.

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?

Front-loaded with the core purpose in the first sentence, then supporting context. Three sentences with essentially no waste, though 'Live calls are kept in a ledger beside the cache' is mildly atmospheric for the information it conveys.

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 no output schema, the description must convey what comes back; it does so at the level of 'spend, this session and this month'. It omits the return format (currency, numeric vs. text) and any cap-remaining detail, which is a minor gap for a simple reporting tool.

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. Nothing in the description misleads about inputs, and there is nothing further to document.

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 (report) and resource (the key's Catalog API spend) with scope qualifiers (this session and this month). It is unmistakably distinct from every sibling, all of which are search/get/download tools rather than budget introspection.

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 supplies the condition that makes the tool relevant ('a key is capped per month and a long sweep can exhaust it'), which implicitly tells the agent to check spend before large operations. It stops short of naming an alternative tool or an explicit when-not-to-use rule, but the single-purpose, zero-parameter nature leaves little routing ambiguity.

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