usage_report

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

Beyond the readOnlyHint/destructiveHint annotations, the description adds valuable context: the scope is local-only, token figures are estimated using a chars/4 approximation, credits depend on an environment variable, and all token/credit numbers are explicitly 'never exact'. This is strong transparency about accuracy and conditional behavior.

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 two sentences, front-loaded with the core purpose, and every piece of information earns its place. No redundancy or filler.

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?

Given the read-only annotations, fully documented schema, and simple report nature, the description covers the essential scope, estimation caveats, and conditional credits. The lack of an output schema is a minor gap, but the description's mention of 'recent calls' provides enough context for expected return content.

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 input schema already describes both parameters fully (since and output_format) with 100% coverage. The description does not add any parameter-specific meaning, so the baseline of 3 applies.

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 clearly identifies the tool as a local usage report covering total runs, per-lane metrics, token estimates, credits, and recent calls. It provides specific scope ('this machine only') that distinguishes it from potentially broader stats tools, though it doesn't explicitly name sibling alternatives.

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 implies when to use it (for local usage stats) but gives no explicit guidance on when not to use it or how it compares to siblings like usage_budget or lane_stats. There are no exclusions or alternative tool references.

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