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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so safety is covered; the description adds genuine behavioral context by stating that a freshly created agent will return an empty list and that create_eval is how entries come into existence. That empty-result disclosure is exactly the kind of non-obvious behavior that prevents an agent from misreading an empty response as an error.

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, zero filler. Scope is front-loaded, and the secondary fact (empty for new agents, create via create_eval) follows rather than competing with the primary statement.

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 an output schema covering return values and annotations covering safety, the description only needs to establish purpose, scope, and the empty-state caveat — all of which it does. It stops short of explaining what a 'test scenario' contains or how many might be returned, but those gaps are minor given the structured fields.

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 coverage is 100% and the single parameter already documents 'Filter by agent ID (optional).' The description reinforces the meaning of omitting it ('or all accessible agents'), but adds no format, syntax, or edge-case detail beyond the schema, which is the expected baseline here.

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 ('List saved test scenarios') and immediately defines the scope ('for an agent (or all accessible agents)'), which tells an agent exactly what this returns and how broad it is. It also names the sibling create_eval as the write counterpart, so list vs. create is unambiguous without opening either schema.

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 the caller a clear selection rule for the optional filter — pass an agent to scope, or omit it for all accessible agents — and routes creation to create_eval. What's missing is any positive exclusion (e.g., when to prefer a different listing tool) or a stated prerequisite such as needing access to the agent, but the when-to-use signal is clear.

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