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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds real behavioral context: the two distinct result shapes (provider+model count vs. model+voice count) and where voice data actually lives. It omits pagination or catalog-size caveats, so not a 5.

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?

Front-loads the resource identity, then splits the two modes into parallel clauses with zero filler. The find_voices pointer is placed last where it is most useful as a routing note.

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?

An output schema exists, so return-value details are not the description's burden. For a single-optional-parameter read tool, the description covers purpose, both modes, and sibling routing, leaving nothing an agent needs to call it correctly.

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 parameter's schema description ('Omit to list every provider first') already conveys the same omit-vs-supply semantics as the description. The description adds no syntax or format detail beyond the schema, so baseline 3 is appropriate.

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 (list) and resource (speech providers, or one provider's models), and explicitly demarcates scope against the sibling find_voices ('Voices themselves come from find_voices'). An agent can distinguish this from find_voices 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?

Explains both invocation modes: no argument returns every provider with model counts, and supplying a provider returns that provider's models. It also routes voice lookups to find_voices. There is no explicit when-not guidance beyond that routing, so it falls just short of a 5.

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