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

Annotations cover the safety profile (readOnly/idempotent/non-destructive), and the description adds real behavioral context beyond them: the three output modes keyed off stem_name/daw/neither (wav+MIDI vs DAW session vs ZIPs), the Premier plan prerequisite, and the absence of credit cost. This is what an agent needs to predict the result.

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?

One dense sentence, front-loaded with the action and the prerequisite, then the per-parameter outcomes. Slightly run-on, but every clause carries information the agent needs.

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 no output schema, the description must characterize the return values, and it does so precisely (download links, and what files each mode returns). Plan and cost constraints are also covered, leaving no material gap.

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 baseline is 3, but the description adds meaning the schema does not: each stem_name yields that stem's WAV and MIDI, each daw value yields one session file, and supplying neither yields ZIPs of all audio and all MIDI. That clarifies the effect of each parameter rather than restating it.

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 ('Get download links from a finished extraction') and anchors it to the sibling that produces its input ('stems_id from mureka_extract_stems'). An agent can distinguish this from mureka_download_song and mureka_extract_stems immediately.

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 says the id must come from mureka_extract_stems and that extraction requires Mureka's Premier plan, plus a credit note ('Free: no new extraction and no Gold'). It does not contrast with mureka_download_song, but the context and prerequisites are clear.

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