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

Annotations cover the safety profile (non-read-only, idempotent, non-destructive), and the description adds meaningful behavior beyond that: the size/duration limits, the requirement to omit the LyricPatch Authorization header on the storage PUT, and the fact that this only reserves an upload rather than transferring bytes. These are non-obvious operational details an agent would otherwise get wrong.

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 tight sentences, front-loaded with the operation and its limits, then the mechanics, then the sequencing. No filler.

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 values need not be explained, and the description still usefully notes the returned URL and headers plus the downstream create_project/ingest_project flow. The remaining gap is the undocumented parameters, particularly idempotency_key.

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% and the description provides no per-parameter meaning for filename, size_bytes, or idempotency_key. It alludes to the 100 MB cap (matching size_bytes maximum) but says nothing about idempotency_key's role in deduplication or the key's format constraints, leaving the most semantically important parameter undocumented.

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+resource ('Prepare a private MP3 upload') with hard constraints (100 MB / 15 minutes max) and the follow-up mechanism ('PUT bytes to returned URL'). Clearly distinguishable from sibling preparation tools like prepare_export and prepare_credit_purchase.

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 names the alternative/next steps ('follow with create_project and ingest_project') and states the condition ('This only reserves an upload'), which tells the agent this is a two-phase flow rather than a completed upload. Also gives an explicit when-not instruction about the Authorization header.

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