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player_set_speed

Set the playback speed multiplier for media in mpv player. Use values like 0.5 for half speed, 1.0 for normal, or 2.0 for double speed.

Instructions

Set playback speed multiplier. 1.0 = normal speed.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
speedYesSpeed multiplier e.g. 0.5, 1.0, 1.5, 2.0

Implementation Reference

  • index.js:394-407 (registration)
    Tool registration definition for 'player_set_speed' including name, description, and inputSchema.
    {
      name: "player_set_speed",
      description: "Set playback speed multiplier. 1.0 = normal speed.",
      inputSchema: {
        type: "object",
        properties: {
          speed: {
            type: "number",
            description: "Speed multiplier e.g. 0.5, 1.0, 1.5, 2.0",
          },
        },
        required: ["speed"],
      },
    },
  • Input schema for player_set_speed: expects a 'speed' number (speed multiplier).
    inputSchema: {
      type: "object",
      properties: {
        speed: {
          type: "number",
          description: "Speed multiplier e.g. 0.5, 1.0, 1.5, 2.0",
        },
      },
      required: ["speed"],
    },
  • Handler logic for 'player_set_speed': ensures mpv is running, sets the 'speed' property via setProperty, and returns a confirmation string.
    case "player_set_speed": {
      await ensureMpv();
      await setProperty("speed", args.speed);
      return ok(`Speed set to ${args.speed}x`);
    }
Behavior3/5

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

With no annotations, the description adds minimal behavioral context beyond the schema, explaining the multiplier concept but not addressing constraints, effects on other state, or error scenarios.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two short, front-loaded sentences with no wasted words; every word earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple one-parameter setter with no output schema, the description is nearly complete, providing purpose and a reference value. Minor omission: no mention of valid ranges or behavior during paused playback.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The schema already covers the parameter with examples (0.5, 1.0, 1.5, 2.0), and the description adds only '1.0 = normal speed' which is helpful but not extensive; baseline 3 due to high schema coverage.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the action ('Set playback speed multiplier') and provides a reference value (1.0 = normal speed), distinguishing it from sibling tools like play, pause, etc.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No explicit guidance on when to use this tool versus alternatives, but the context of sibling tools makes it implied; missing explicit when-not or alternatives.

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

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