Session Statistics

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering safety. The description adds valuable behavioral detail by listing exactly what statistics are returned (total bytes, breakdown by tool, call counts, estimated token usage, context savings ratio), which goes beyond the annotations and helps the agent understand the tool's output.

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, well-structured sentence that front-loads the core purpose ('Returns context consumption statistics') and then enumerates the specific stats in a compact list. No filler or redundant information is present.

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 (no parameters, no output schema), and the description fully covers its scope, behavior, and return values. It lists the types of statistics provided, which is sufficient for an agent to understand what it will receive. Annotations cover safety traits, so no further information gaps exist.

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 description does not need to explain parameter meanings. The schema coverage is trivially 100% with an empty properties object. Per the rubric, baseline for 0 parameters is 4, and the description adequately complements the schema by explaining what the tool reports without needing parameter documentation.

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 the tool returns context consumption statistics for the current session, with a specific verb ('Returns'), resource ('context consumption statistics'), and scope ('current session'). This distinguishes it from siblings like ctx_execute or ctx_search, which perform actions or queries rather than reporting statistics.

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?

Usage is implied rather than explicitly stated. The description tells what it does but does not provide explicit 'when to use' or 'when not to use' guidance, nor does it mention alternatives. While the purpose makes its use case obvious, there is no direct comparison with sibling tools or contextual exclusions.

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