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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so the safety profile is covered without the description. The description's added content (status, parameters, download URL, expiry) largely restates what the output schema already documents, so it contributes little behavioral context beyond the structured fields.

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?

A single efficient sentence that leads with the action and resource, then enumerates returns. Every clause is short and no filler is present, though the returns enumeration partly duplicates the output schema.

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 an output schema and annotations present, the definition can stay lean, and it does. But for a tool sharing a crowded namespace with list_tracks, wait_for_track and search_library, the absence of any routing or timing guidance leaves a real 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 description coverage is 100%, so the critical nuance — that track_id accepts either a track id or a session id, and by_session_id must be set in the latter case — is fully documented in the schema. The description adds nothing about parameters, which is the baseline 3 for full schema coverage.

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 (Fetch) and resource (one track) plus the payload contents, so the agent knows it retrieves a single track object. It does not, however, differentiate itself from siblings like list_tracks, wait_for_track, or search_library.

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?

Usage is only implied by 'one track' — the single-item counterpart to list_tracks. There is no guidance on when to use this versus wait_for_track (which likely polls until ready) or search_library, and no mention of prerequisites.

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