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

Goes well beyond the annotations: it discloses that playback continues uninterrupted, that the change lands on a musical boundary, that errors are reported back if the player responds within seconds, and the subtle gotcha about shipping a merge rather than a new start value for remember() state. This is exactly the kind of context annotations cannot convey.

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 and dense with useful content; the precondition and the timing behavior come first. A few clauses restate the schema's quantize values, which is minor redundancy but not wasteful enough to hurt.

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 mutation tool with no output schema, it covers precondition, timing semantics, result/error feedback, a state-mutation caveat, and points to the guide for the tricky case. An agent has everything needed to invoke 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%, so the baseline is 3, but the description adds real meaning: the quantize value should match phrase length (with a concrete example), and code must be the WHOLE pattern rather than a fragment. This exceeds what the schema text alone communicates.

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: it swaps new code into a live session's player while playback continues. The phrase 'Only for a live session' plus 'as for play-live-pattern' implicitly contrasts it with the sibling that starts a live session, though it never names that alternative 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?

Gives a clear precondition ('only for a live session') and usage guidance for quantize tied to musical phrasing ('8-bar phrase → 8'). It does not explicitly say when not to use it or name the tool to create a session first, leaving that inference to the agent.

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