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

Annotations already declare readOnly, idempotent, and non-destructive behavior, and the description adds that this is a simulation without side effects, what data it reports, and that it needs a key with a docs link. This gives an agent behavioral and auth context beyond the structured fields.

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 sentences carry action, output, use case, and auth requirement, with no filler or redundancy. The key information is front-loaded.

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 single-parameter, read-only simulation tool the description is sufficient: it explains what happens, what the agent will see, why to call it, and the auth prerequisite. With no output schema, the description's summary of return values is especially valuable and it is present.

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 sole parameter 'rule' is fully documented in the schema ('The rule to try'), and the description reinforces it by talking about testing a rule, but it does not add syntax or format details. With 100% schema coverage, this meets the baseline without needing extra compensation.

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 names the specific action (replays the last seven days against a rule) and the delivered results (how often it would hit, last ten hits), and explicitly says it does not set the rule — distinguishing it from sibling create_rule. The title reinforces the purpose, but the description alone is sufficient.

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 'Use it to see how noisy a rule is first' gives a concrete use case, and 'without setting it' implies this is a safe pre-check before creating a rule. It does not explicitly name create_rule as the follow-up alternative, but the context is clear.

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