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

Annotations mark this as a non-read, non-destructive mutation, and the description adds genuinely new behavior: writes are appended and existing scenarios are preserved, which tells the agent this is additive rather than a replace/overwrite. It does not describe any permission requirements or whether the change is reversible/undoable.

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?

Three sentences, front-loaded with the action and target, then usage, then the append guarantee. No filler or redundancy.

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 an additive mutation with full schema coverage and annotations declaring the safety profile, the description supplies the key missing piece (append semantics and a purpose for the added scenarios). An output schema does not exist, so return values are not needed; the only minor gap is no note on limits or whether added scenarios take effect immediately.

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% with 3 parameters, so the schema already documents agentId, scenarios, and the nested scenario fields including isSafetyCritical. The description adds no syntax, format, size limits, or batching guidance beyond what the schema provides, so baseline 3 applies.

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 states a specific verb and resource ('Add custom regression test scenarios') and scopes the target ('an agent's existing golden suite'), which separates it from suite-creation or read paths. It does not name the sibling get_regression_suite explicitly, so an agent must infer the read/write split from the sibling list.

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 gives a clear use case ('strengthen the regression suite with scenarios targeting specific behaviors') plus concrete examples (human escalation, multi-language, support routing). There is no when-not guidance and no explicit pointer to the read sibling for reviewing an existing suite.

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