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

With no annotations, the description carries the full burden. It discloses key behavioral traits: the one-entry-per-(service, metric) expansion, the meaning of each entry's fields, the per-service lastSeen semantics, and filtering behavior. It does not mention response limits, authentication, or error cases, but the core behavior is well covered.

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 well structured and economical: it starts with the core purpose, then explains usage context, then lists params, and finally states the return type. Every sentence earns its place without redundancy or fluff.

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?

For a list tool with three optional params and no output schema, the description provides a complete picture: the return format, entry cardinality, field meanings, filtering options, and even a specialized use case. The only minor gaps are lack of pagination/limit details and error behavior, but these are not critical for initial tool selection.

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 all three parameters with clear definitions (e.g., 'Filter to a specific service name', 'ISO-8601 instant inclusive/exclusive'). The description adds minimal extra value by framing the time window as 'seen within the range', but it does not introduce format details or constraints beyond the schema. Baseline 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 clearly states the tool lists available metrics with a specific per-(service, metric) pair structure. It distinguishes itself from the sibling 'metrics' tool by explicitly saying to use it 'before calling metrics' and by clarifying the unique entry expansion behavior.

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?

It explicitly instructs to use this tool to discover metrics and which services emit them before calling metrics, and it names an alternative tool. It also provides a concrete use case (dead-emitter detection) that helps the agent decide when it's appropriate.

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