Decent-Sampler Drums MCP Server

Instructions

Implementation Reference

• src/drum-controls.ts:129-153 (handler)

  The main handler function that executes the tool logic: validates drum control configurations (pitch and envelope settings) and generates an AdvancedDrumKitConfig with global drumControls and empty drumPieces for further processing.
  export function configureDrumControls(config: DrumControlsConfig): AdvancedDrumKitConfig { // Validate all drum configurations for (const drum of config.drums) { validatePitchSettings(drum); validateEnvelopeSettings(drum); } // Create the drum kit configuration return { globalSettings: { drumControls: config.drums.reduce((acc, drum) => ({ ...acc, [drum.name]: { ...(drum.pitch && { pitch: drum.pitch }), ...(drum.envelope && { envelope: drum.envelope }) } }), {}) }, drumPieces: config.drums.map(drum => ({ name: drum.name, rootNote: drum.rootNote, samples: [] // Let caller provide samples })) }; }
• src/drum-controls.ts:34-60 (schema)

  TypeScript interfaces defining the input schema for drum controls: DrumPitchConfig, DrumEnvelopeConfig, DrumConfig, DrumControlsConfig. Used for type checking and validation.
  export interface DrumPitchConfig { default: number; min?: number; max?: number; } export interface DrumEnvelopeConfig { attack: number; decay: number; sustain: number; release: number; attackCurve?: number; decayCurve?: number; releaseCurve?: number; } export interface DrumConfig { name: string; rootNote: number; // Required instead of defaulting pitch?: DrumPitchConfig; envelope?: DrumEnvelopeConfig; } export interface DrumControlsConfig { drums: DrumConfig[]; }
• src/index.ts:123-188 (schema)

  JSON Schema defining the input validation for the MCP tool 'configure_drum_controls', matching the TypeScript types.
  inputSchema: { type: "object", properties: { drumControls: { type: "object", additionalProperties: { type: "object", properties: { pitch: { type: "object", properties: { default: { type: "number", description: "Default pitch in semitones (0 = no change)" }, min: { type: "number", description: "Minimum pitch adjustment (e.g. -12 semitones)" }, max: { type: "number", description: "Maximum pitch adjustment (e.g. +12 semitones)" } }, required: ["default"] }, envelope: { type: "object", properties: { attack: { type: "number", description: "Attack time in seconds" }, decay: { type: "number", description: "Decay time in seconds" }, sustain: { type: "number", description: "Sustain level (0-1)" }, release: { type: "number", description: "Release time in seconds" }, attackCurve: { type: "number", description: "-100 to 100, Default: -100 (logarithmic)" }, decayCurve: { type: "number", description: "-100 to 100, Default: 100 (exponential)" }, releaseCurve: { type: "number", description: "-100 to 100, Default: 100 (exponential)" } }, required: ["attack", "decay", "sustain", "release"] } } } } }, required: ["drumControls"] }
• src/index.ts:715-752 (registration)

  MCP CallToolRequestSchema dispatch case that handles the tool call: transforms input arguments to DrumControlsConfig, invokes the handler, generates XML output via generateGroupsXml, and handles errors.
  case "configure_drum_controls": { const args = request.params.arguments; if (!args || typeof args !== 'object' || !args.drumControls) { throw new McpError( ErrorCode.InvalidParams, "Invalid arguments: expected object with drumControls" ); } try { // Convert the input format to our DrumControlsConfig format const drumControlsConfig: DrumControlsConfig = { drums: Object.entries(args.drumControls).map(([name, controls]) => ({ name, ...(controls as any) })) }; // Configure and validate the drum controls const config = configureDrumControls(drumControlsConfig); // Generate XML with the validated configuration const xml = generateGroupsXml(config); return { content: [{ type: "text", text: xml }] }; } catch (error: unknown) { if (error instanceof McpError) throw error; const message = error instanceof Error ? error.message : String(error); throw new McpError( ErrorCode.InternalError, `Failed to configure drum controls: ${message}` ); } }
• src/index.ts:103-189 (registration)

  Tool registration in ListToolsRequestSchema response: defines name, description, and inputSchema for discovery by MCP clients.
  { name: "configure_drum_controls", description: `Configure global pitch and envelope controls for each drum type. This tool will: - Add per-drum pitch controls with customizable ranges - Configure ADSR envelope settings for natural decay control - Generate proper XML structure for global drum controls Error Handling: - Validates pitch range values (min/max must be valid numbers) - Ensures envelope times are positive values - Verifies curve values are within -100 to 100 range - Returns detailed error messages for invalid configurations Success Response: Returns XML structure containing: - Global controls for each drum type - MIDI CC mappings for real-time control - Properly formatted parameter bindings`, inputSchema: { type: "object", properties: { drumControls: { type: "object", additionalProperties: { type: "object", properties: { pitch: { type: "object", properties: { default: { type: "number", description: "Default pitch in semitones (0 = no change)" }, min: { type: "number", description: "Minimum pitch adjustment (e.g. -12 semitones)" }, max: { type: "number", description: "Maximum pitch adjustment (e.g. +12 semitones)" } }, required: ["default"] }, envelope: { type: "object", properties: { attack: { type: "number", description: "Attack time in seconds" }, decay: { type: "number", description: "Decay time in seconds" }, sustain: { type: "number", description: "Sustain level (0-1)" }, release: { type: "number", description: "Release time in seconds" }, attackCurve: { type: "number", description: "-100 to 100, Default: -100 (logarithmic)" }, decayCurve: { type: "number", description: "-100 to 100, Default: 100 (exponential)" }, releaseCurve: { type: "number", description: "-100 to 100, Default: 100 (exponential)" } }, required: ["attack", "decay", "sustain", "release"] } } } } }, required: ["drumControls"] } },