Decent-Sampler Drums MCP Server

Instructions

Implementation Reference

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

  The core handler function that validates and configures drum controls (pitch and envelope) for each drum, producing an AdvancedDrumKitConfig object.
  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/index.ts:103-189 (registration)

  MCP tool registration in ListToolsRequestHandler, defining the tool name, description, and JSON input schema for validation.
  { 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"] } },
• src/drum-controls.ts:34-60 (schema)

  TypeScript interfaces defining the schema for DrumControlsConfig, DrumConfig, DrumPitchConfig, and DrumEnvelopeConfig used by the handler.
  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:715-752 (handler)

  MCP CallToolRequestHandler case for 'configure_drum_controls' that validates input, converts format, calls the core handler, generates XML output, 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/drum-controls.ts:61-128 (helper)

  Helper validation functions for pitch and envelope settings used by the configureDrumControls handler to ensure valid configurations.
  function validatePitchSettings(drum: DrumConfig): void { if (!drum.pitch) return; const { default: defaultPitch, min, max } = drum.pitch; // Validate min/max if provided if (min !== undefined && max !== undefined && min > max) { throw new Error( `Invalid pitch range for drum "${drum.name}": min (${min}) cannot be greater than max (${max})` ); } // Validate default is within range if (min !== undefined && defaultPitch < min) { throw new Error( `Invalid default pitch for drum "${drum.name}": ${defaultPitch} is below minimum ${min}` ); } if (max !== undefined && defaultPitch > max) { throw new Error( `Invalid default pitch for drum "${drum.name}": ${defaultPitch} is above maximum ${max}` ); } } function validateEnvelopeSettings(drum: DrumConfig): void { if (!drum.envelope) return; const env = drum.envelope; // Validate time values are positive if (env.attack < 0) { throw new Error( `Invalid attack time for drum "${drum.name}": ${env.attack}. Must be >= 0` ); } if (env.decay < 0) { throw new Error( `Invalid decay time for drum "${drum.name}": ${env.decay}. Must be >= 0` ); } if (env.release < 0) { throw new Error( `Invalid release time for drum "${drum.name}": ${env.release}. Must be >= 0` ); } // Validate sustain level is between 0 and 1 if (env.sustain < 0 || env.sustain > 1) { throw new Error( `Invalid sustain level for drum "${drum.name}": ${env.sustain}. Must be between 0 and 1` ); } // Validate curve values if provided const validateCurve = (value: number | undefined, name: string) => { if (value !== undefined && (value < -100 || value > 100)) { throw new Error( `Invalid ${name} curve for drum "${drum.name}": ${value}. Must be between -100 and 100` ); } }; validateCurve(env.attackCurve, 'attack'); validateCurve(env.decayCurve, 'decay'); validateCurve(env.releaseCurve, 'release'); }