playMusic

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

With no annotations, the description carries the full burden of behavioral disclosure. It states that device selection is automatic, which is a useful behavioral trait. However, it does not disclose what happens if no device is available, whether it replaces the current queue or just starts playing, or if it requires a premium subscription. The core side effect (starting playback) is clear, but other behavioral aspects are omitted.

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, front-loaded with the primary purpose, and each sentence earns its place. It efficiently covers the main usage, parameter details, and auto-selection behavior without redundancy or fluff.

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?

The tool has 7 parameters, no annotations, and no output schema. The description covers the URI-based approach and aliases, but it does not explain the alternative to use id+type to identify the item, nor does it mention offset usage or what the tool returns. This leaves gaps in understanding for an agent trying to invoke it correctly in all scenarios, especially since no parameters are required.

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% (all 7 parameters have descriptions), so the baseline is 3. The description adds value by clarifying aliases (device_id is an alias for deviceId, context_uri is an alias for uri) and emphasizing that deviceId is optional because auto-selection happens. It also gives concrete URI examples. This goes slightly beyond the schema, but could further explain the id/type alternative and offset behavior.

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 starts with a clear verb and resource: 'Start playing a Spotify track, album, artist, or playlist.' It distinguishes this tool from siblings like pausePlayback, resumePlayback, skipToNext, and addToQueue by focusing on initiating playback of a specific item. The purpose is unmistakable and specific.

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 provides clear usage context: pass a Spotify URI, device auto-selected, optional deviceId. However, it does not explicitly say when to use this tool versus closely related siblings like resumePlayback (for resuming paused playback) or skipToNext. No alternatives or exclusions are mentioned, leaving potential ambiguity in tool selection.

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