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

Annotations already flag destructive=true, idempotent=false and openWorld=true; the description reinforces and explains this with 'calling this again replaces the running one rather than opening a second', and adds non-obvious billing behavior — metered by seconds played, reported after the fact, quota can be overshot.

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-loads the action and return value, then two tight paragraphs covering the when-to-use case and the runtime constraints. No filler sentences; every clause carries operational meaning.

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 present, return shape need not be explained, yet the URL is still mentioned. The single-stream, replace-on-recall and metered-billing details give an agent everything needed to call this correctly and anticipate side effects.

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 75%, with intensity, stream_type and playlist_index documented in the schema and bitrate left undocumented in both places. The description adds no parameter-level detail (types, units, defaults), so it does not compensate for the gap or exceed the schema baseline.

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 ('Open an endless, non-repeating music stream') plus the return value ('return its URL'), and implicitly contrasts with the generate_track family by emphasizing a continuous stream rather than discrete tracks.

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 'use this instead of generating tracks when the music should never stop and never loop', then enumerates concrete scenarios (workout app, game, focus tool, venue). The alternative and the selecting condition are both named.

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