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

With readOnlyHint=false, the agent knows a write occurs, but the description usefully clarifies that the write is internal ('save them as a bio A/B test') and that 'Nothing is changed on the platform itself' — a non-obvious scope boundary. It also discloses the cost profile ('Uses one AI text action'). It stops short of noting that the call is non-idempotent, i.e. that repeated invocations create additional A/B tests.

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 sentences, front-loaded with the core action and output shape, followed by the two facts an agent can't get from structured fields: AI-action cost and platform-side safety. No filler or restated title.

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 2-parameter tool with no output schema, the description covers what is produced, where it is stored, and its side-effect boundary. It leaves implicit that a trained voice model is a prerequisite (implied by 'in the user's trained voice') and how the resulting A/B test is later retrieved or evaluated, but nothing essential to calling it correctly is missing.

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% and both parameters are documented there, including that current_bio is 'the bio the user has now, to improve on.' The description adds only that current_bio is optional, which the schema already conveys via the required list. Baseline 3 is appropriate when the schema does the heavy lifting.

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?

States a specific verb and resource ('Generate two profile-bio variants for one platform') plus the distinguishing output ('save them as a bio A/B test'), which separates it from siblings like generate_persona_post or generate_posts. The A/B framing and the A-authority / B-curiosity split tell an agent exactly what comes back.

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 conditional for the optional parameter ('Optionally pass the current bio to improve on'), which is useful, but offers no when-to-use guidance relative to siblings such as generate_persona_post, generate_posts, or train_voice_model. Usage must be inferred from the name and the description's scope.

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