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

Annotations only say destructiveHint=true; the description explains exactly what is destroyed (everything not in the submitted list) and adds behavior the annotations cannot express: max 5 items with unique ids, premium voices stripped on save, a read-before-write guard that aborts if the read fails, and optimistic concurrency via expected_updated_at. It also enumerates the failure modes (conflict, conflict_unchecked) and the exact return shape, so the agent can anticipate rejection conditions before calling.

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-loaded with the replacement warning, then structured Args/Returns sections, with no filler sentences. Minor ding: the first paragraph is a run-on chaining several independent constraints with commas and 'and', and the leading 'Free.' fragment is orphaned rather than integrated into the cost 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?

For a destructive two-parameter write with no output schema, the definition covers everything an agent needs: destructive semantics, size and uniqueness constraints, side effects on premium voices, the concurrency precondition, error codes with remediation, and the success return shape. Nothing material is left to inference.

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 description coverage is 0%, so the description carries the full burden and does: it names both parameters, states the 5-item cap and id uniqueness, spells out the inner object fields (id, name, look:{preset, prompt}, voice, captions, aspect, music_genre, length_s, watermark_key), and explains that expected_updated_at must come from a prior styles_get. This is meaning the JSON schema (additionalProperties:{} with no per-field docs) cannot convey.

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 ('REPLACES the whole list of style presets') and immediately bounds the scope: it is a full-replacement write, not a merge or an append. The parenthetical '(from styles_get, changed)' distinguishes it from the read sibling without ambiguity.

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?

Gives an explicit when-to-use chain: read via styles_get, modify, then send the complete list here. It also states the consequence of getting it wrong ('a partial list deletes the rest') and routes back to styles_get on conflict, so the agent knows both the correct entry path and the recovery path.

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