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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds behavioral context the annotations cannot: what omitting 'assistant' actually does ('gives auto — the general specialist unless routing picks an expert') and what the general specialist covers. It does not mention output shape or ordering, but the read-only profile is fully declared elsewhere.

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?

The purpose and the usage rule are front-loaded, which is good, but the middle of the description enumerates all ten assistant names and ids — data the tool itself returns at call time. That enumeration duplicates the (unshown) return value and inflates the description well past what an agent needs before invoking it.

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?

There is no output schema, so the description carries the burden of describing return values — and it does, listing every assistant and id along with the two grouping modes. Combined with the routing rule, an agent has everything needed to call this and act on the result.

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 tool takes zero parameters, so the baseline of 4 applies. The description goes further by explaining the semantics of the 'assistant' argument on the sibling tools it feeds, mapping ids to concrete names, which is genuine added meaning rather than restatement.

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 opening sentence names the verb and resource precisely ('List built-in assistants') and immediately breaks the resource into its two enumerable categories (by_job, built_in) with their distinguishing attributes (jobs with skills vs frameworks). No sibling tool in the list returns assistants, so there is no ambiguity to resolve.

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 states exactly when to call it ('before picking an id for assistant on create_conversation or send_message') and, unusually, when NOT to ('not needed when their description already shows the right id'). It then supplies a decision rule for job id vs framework id vs omitting the assistant entirely, leaving nothing to inference.

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