Adjust Spotify playback volume to a specific percentage between 0 and 100, optionally targeting a device. Requires Spotify Premium.
Set the playback volume to a specific percentage (0-100). Requires Spotify Premium.
| Name | Required | Description | Default |
|---|---|---|---|
| deviceId | No | The Spotify device ID to set volume on | |
| volumePercent | Yes | The volume to set (0-100) |
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden, and it does add one genuinely useful behavioral fact: the Spotify Premium requirement. It still omits whether this targets the active device by default, what happens if deviceId is omitted, and whether it errors on free accounts.
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?
Two short sentences, front-loaded with the core action and range, with the prerequisite appended. Nothing is wasted.
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 tool with no annotations and no output schema, the description covers purpose and the Premium prerequisite but leaves the device-targeting behavior and the adjustVolume relationship unexplained.
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 both parameters are already documented in the schema. The description only restates the 0-100 range and adds no semantics beyond it, which is the baseline 3 case.
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 (Set) and resource (playback volume) with the value range, so the action is unambiguous. However, it does not distinguish itself from the sibling tool adjustVolume, which an agent must choose between.
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?
No when-to-use guidance is given. The presence of a near-identical sibling (adjustVolume) makes the absence of any routing rule — absolute set vs. relative adjust — a real gap.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.