play

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

With no annotations, the description carries the full behavioral burden; it does disclose the default behavior when no URI is passed (resume current playback), which is real value. It omits other important traits: that playback control typically requires a premium/authenticated account, that starting a new track replaces the current playback context, and any error/queue side effects.

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?

Three short sentences, front-loaded with the primary action, followed by the fallback behavior and the format examples. Every sentence adds information with no redundancy.

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?

For a single-optional-parameter tool with an output schema (so return values need not be explained), the description covers purpose, accepted identifier format, and no-argument behavior. It is nearly complete; only authentication requirements and the side effect of replacing current playback are missing.

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 0% and the single parameter has no description, so the tool description must compensate — and it does, providing two concrete URI format examples and explaining what happens when the optional parameter is omitted (resume). This goes meaningfully beyond the bare 'string, default ""' schema.

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 (play) and resource (song or playlist) plus the required identifier format (spotify:track:xxx / spotify:playlist:xxx). Its role is unambiguous against siblings like pause, next_track, and search_track, which are clearly different operations.

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?

It gives one conditional usage rule — omit the URI to resume current playback — which is genuinely useful. However, it never points to alternatives (e.g. using search_track/search_playlist to obtain a URI, or pause to stop), so routing guidance is only implied.

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