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

The annotations already provide readOnlyHint=true and openWorldHint=true, so the agent knows this is a safe read operation. The description adds valuable context: it reveals that the result ordering is by an internal catalogue key, explicitly stating it is NOT an audience metric (e.g., popularity). It also mentions that each result includes full audio features, which sets expectations about the response richness. This goes beyond what annotations alone would 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?

The description is three sentences, compact and comprehensive. The first sentence immediately states the purpose and use case, making it front-loaded. The second sentence details the key parameter format and return ordering behavior, and the third sentence provides a clear alternative. No fluff, every sentence earns its place.

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?

Given this is a read-only query tool with only 2 parameters, the description covers everything: the filtering capability, the parameter formats, the output characteristics (full audio features, ordering), and the workflow with siblings. The output schema exists, so return structure is presumably documented elsewhere. The description is fully sufficient for an agent to call this 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 description coverage is 100%, and the 'key' parameter description in the schema already lists the accepted formats (Camelot, Open Key, key name). The description reaffirms these formats and adds that it accepts formats like '8A', '1m', 'A-Minor', giving concrete examples. For the 'limit' parameter, the default and max are clear from schema. The minimal additional info beyond schema earns a baseline 3.

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?

The description clearly states the action (find catalog tracks), the resource (tracks), and the specific filter (musical key). It explicitly mentions the use cases (harmonic mixing, key-locked playlists) and differentiates from sibling find_tracks_by_bpm (which filters by BPM not key) and find_compatible_keys (which finds key compatibility, not tracks). This is a specific and unambiguous purpose.

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?

The description explicitly tells the agent when to use this tool (when you need tracks in a specific key) and when to use find_compatible_keys first (to discover which keys mix well). This clear routing to the sibling reduces ambiguity and provides practical workflow guidance, which is exemplary.

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