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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds meaningful behavioral context: 'Free' indicates no monetary cost, and listing 'billing status' implies the tool surfaces financial/account state. This goes beyond the annotation safety profile and gives the agent useful expectations about what the operation checks.

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 a single, information-dense sentence. It front-loads the primary action ('Check your current usage and quota') and immediately follows with the specific data points. Every word earns its place; no fluff, no irrelevant 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 is simple (one optional boolean parameter) and has an output schema, so the description doesn't need to explain return values. It covers the essential scope (usage, quota, rate limits, billing), mentions cost ('Free'), and is entirely self-contained. The annotations and schema fill any remaining gaps, so no further context is needed.

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 covers 100% of the parameter description ('Include hash-chain integrity check and latest provenance epoch'). The tool description itself does not mention the parameter, but since the schema already provides a clear semantic explanation, the description adds no extra value here. Baseline of 3 is appropriate.

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 starts with a specific verb 'Check' and clearly identifies the resource: 'your current usage and quota'. It enumerates the exact data points (calls used/remaining, tier, rate limits, billing status), making it unmistakably distinct from sibling tools like health or verify, which focus on system status or cryptographic verification.

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 context is clear: use this tool to inspect usage and quota. It doesn't explicitly name alternatives or exclusions, but the description's specificity ('calls used, calls remaining, tier, rate limits, billing status') implicitly sets it apart from sibling tools. A 4 is appropriate because it lacks an explicit 'use instead when...' clause, but the intended usage is unambiguous.

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