invariance_metrics_agents

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

Annotations already declare readOnlyHint=true, so the read-only nature is covered. The description adds that it returns aggregated metrics over a time window, which is useful context. However, it does not disclose details like default window behavior or data format beyond the schema, so it adds modest value but no contradictions.

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?

Two short, dense sentences with no filler. The core purpose is front-loaded, and the usage hint is appended without redundancy. Every word earns its place.

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 simple read-only rollup with one optional parameter and no output schema, the description states the returned metrics (run counts, node counts, cost) and the per-agent scope, which is sufficient for an agent to understand what it will receive. Minor gaps like pagination or aggregation details are not critical given the tool's simplicity.

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?

Schema description coverage is 100% – the only parameter window_hours has a clear description including default and max. The tool description does not add any additional parameter semantics, so the baseline of 3 applies because the schema carries the meaning.

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 a specific verb ('rollup') and resource ('per-agent usage') with explicit metrics (run counts, node counts, cost). It also conveys the intended comparison use case, distinguishing it from sibling tools like invariance_metrics_overview or invariance_run_metrics which target different scopes.

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 phrase 'Useful for agent-by-agent comparison' gives a clear when-to-use scenario, but it does not mention alternatives or provide exclusions (e.g., when to use run-level metrics instead). This leaves some ambiguity for an agent choosing among many metric-related siblings.

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