getSessionUsage

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

Annotations already declare readOnlyHint=true. The description adds value by specifying exactly what is estimated (schema size, call counts, largest tool results), providing context beyond the annotation. There is no contradiction.

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?

A single sentence of 12 words that is front-loaded with the core purpose. Every word earns its place; no extraneous information.

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 description is sufficient for a simple read-only tool. It covers the return value components. However, it could be slightly more explicit about whether the estimate is cumulative or per-request, though 'for this session' implies cumulative.

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 is empty with 0 parameters, so schema coverage is 100% trivially. The description adds meaning by explaining what the output contains (estimates of various metrics), which is valuable beyond the schema.

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 states it provides a 'Token usage estimate for this session' and lists the components (schema size, call counts, largest tool results). This distinguishes it from other get* siblings like getActivityLog or getAnalyticsReport.

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 usage for retrieving session token usage but does not provide explicit when-to-use or when-not-to-use guidance, nor does it mention alternatives like getActivityLog for logs.

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