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

Annotations already establish readOnlyHint=true and destructiveHint=false, so the description doesn't need to re-declare safety. It adds value beyond them by disclosing result ordering (most-used first), the at-least-one-input precondition, and the paging mechanism via cursor. It does not say anything about page size or what fields a voice record carries.

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?

A single well-formed sentence with the resource, ordering, precondition and paging clause — no filler, and the key constraint sits in the middle rather than being buried. Nothing here is redundant with a title of the same name.

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 no output schema, the description carries the burden of describing results, and it conveys ordering and paging well enough to call the tool correctly. Minor gaps remain: page size, whether filters combine with AND, and whether query matches names versus descriptions are left to the schema. Adequate but not exhaustive for a five-parameter search.

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 80%, so per-parameter meaning is mostly already documented. The description still contributes the cross-parameter constraint (query OR a filter must be supplied) that no individual schema field expresses, and confirms cursor semantics as 'next page of the same search'. The untyped/undescribed remainder is small.

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 ("Search the ElevenLabs voice library") plus the default ordering ("most-used voices first"), which tells an agent what kind of result set to expect. It does not name the obvious sibling list_voices, so the agent must infer that browsing without a query belongs there rather than here.

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?

"Needs a query or a filter" is genuine usage guidance that resolves the schema's zero-required ambiguity — the agent knows it cannot call this with an empty object. "Page with `cursor`" gives the iteration procedure. What's missing is an explicit exclusion pointing to list_voices for unfiltered browsing.

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