list_singers

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

With no annotations, the description carries the full burden, and it does disclose one valuable behavioral trait: entries lacking a default phonemizer receive a 'suggested_phonemizer' that is explicitly labelled a guess requiring confirmation via rank_phonemizers. That caveat is genuinely useful. It does not disclose whether the call triggers a rescan of installed singers, or whether it fails when OpenUtau is not running.

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 English portion is well front-loaded: return fields first, then the caveat about the guessed phonemizer. But the entire text is then repeated verbatim in Japanese, roughly doubling length without adding any information for an agent that has already read the first half. Content is tight; the duplication is the flaw.

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 must describe the return shape itself — and it does, field by field, including the conditional suggested_phonemizer. For a zero-argument list tool this is nearly complete; only the scan/refresh semantics and any failure mode are left unstated.

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 there is nothing for the description to disambiguate; baseline 4 applies. The schema is an empty object, consistent with the description's no-argument framing.

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 concrete verb and resource ('Singers OpenUtau has loaded') and enumerates exactly what each entry contains: id, name, type, location, default phonemizer, supported renderers. That is enough to distinguish it from a single-singer getter. It stops short of naming how it differs from the sibling 'refresh_singers', so it is clear but not fully differentiated.

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?

Usage is implied rather than stated: an agent can infer this is the read-only inventory tool, and there is one concrete routing hint — confirm a suggested phonemizer with 'rank_phonemizers'. However, nothing says when to call this versus 'refresh_singers' or 'list_phonemizers', and no preconditions (e.g. OpenUtau running) are given.

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