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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds behavioral context beyond this: the response combines multiple types of music-history data, limit applies across the combined response, playableOnly restricts rows to ChatGPT-playable audio, and allowBuild=false plus allowSave=false preserves a read-only request. No contradiction with the annotations is present.

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 description is compact and front-loaded, beginning with the most important instruction ('Call exactly once') before moving into parameter behavior. The sentence enumerating the combined payload is informative rather than filler, and there is little redundant phrasing.

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 explanation is unnecessary. The description covers all invocation-relevant context: exact call count, date modes, limit scope, playableOnly behavior, read-only flag combinations, and how this tool relates to other calls. An agent has enough information to call music_today 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 description coverage is 100%, so the baseline is 3 even without parameter info in the description. The description mainly restates what the schema already says, such as dateMode=today omitting date and limit being the combined maximum. It adds no fundamentally new parameter semantics beyond the schema.

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 leads with a precise directive ('Call exactly once for a 'today in music' or dated music-history request') and lists the combined payload components: anniversaries, birthdays, releases, chart context, and stories. It closes by positioning the tool as 'the only dated-music tool in the current schema,' clearly distinguishing it from siblings.

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?

It gives an explicit when-to-use trigger and an explicit when-not-to-split instruction: use one combined call rather than separate history, releases, charts, or shows calls. It also provides parameter-level usage direction (dateMode=today vs explicit, limit caps, playableOnly filtering, and read-only flags), leaving little to inference.

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