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

Annotations already cover the read-only profile, and the description adds genuinely new context: the call is free and its result is consumed downstream by tegas_start_video. It does not mention pagination or ordering, but with output schema present and readOnlyHint declared, this is a solidly informative description.

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?

Three short sentences, front-loaded with 'Free.' and the resource statement, followed by the practical consequence of the call. Zero wasted text.

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 an output schema available the description need not explain return values, and it covers cost, optionality, and downstream use. The only gap is the missing 'tr' language and the undocumented default, both of which matter for a single-parameter tool.

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 0%, so the description must carry parameter meaning, and it does list languages -- but it omits 'tr', which is present in the schema enum, creating a small mismatch with the actual accepted values. It also never mentions the 'ru' default, so the description is only partially compensating for the empty schema descriptions.

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 -- 'List voice-over voices for a language' -- and enumerates the supported languages, so the agent knows exactly what comes back (voice items). It does not need to differentiate from siblings since no other tool deals with voices, though it could have named the relationship to tegas_start_video more explicitly.

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?

Explicitly tells the agent that calling this is optional because omitting `voice` yields the default natural voice, and it routes the output to `tegas_start_video` as the `voice` parameter. That is a clear when-to-use / when-not-to-use statement plus the destination of the result.

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