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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint, so the safety profile is well covered. The description adds meaningful context beyond annotations by explaining identity resolution from the bearer token and the zeroed shape for anonymous callers, which is a non-obvious behavioral trait. This is solid but not extensive, earning a 4.

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 three sentences, each with clear purpose: what it returns, how identity works, and when to use it. It is front-loaded with the core purpose and avoids redundant phrases. No filler or repetition of the title/name.

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 fully compensates by itemizing the return metrics (total calls, success rate, p50 latency, per-tool counts) and describing the anonymous case. Combined with strong annotations and zero parameters, this is complete for an agent to select and invoke the tool correctly.

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 schema coverage is trivially 100%. With 0 params, the baseline is 4 and no parameter description is needed. The description focuses on output composition and usage context, which 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 opens with a specific verb and resource: 'Return the caller's own trailing 30-day MCP tool-usage summary.' It enumerates exactly what the summary contains (total calls, success rate, p50 latency, per-tool counts), clearly distinguishing this tool from siblings like get_my_private_feed or get_trending_topics.

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 gives clear use cases: 'self-budget against rate limits, audit which tools your agent actually uses, or decide whether a paid tier is worth the spend.' It also explains the auth context (OAuth bearer token, anonymous zeroed shape), but does not explicitly state when not to use it or name alternatives. Clear context, no exclusions, so a 4 is appropriate.

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