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mcp_opendaw_create_ratchet

Create a ratchet effect with accelerating or decelerating repeated notes for musical builds and fills. Adjust pitch, velocity, and subdivision rate to craft dynamic sequences.

Instructions

Create a ratchet — repeated notes with changing subdivision rate.

A ratchet (also called "accelerando repeat" or "Bach ratchet") is a series of repeated notes where the spacing between notes gradually decreases (accelerate) or increases (decelerate), creating a sense of acceleration or deceleration. Used extensively in Baroque music (Bach cadences), electronic build-ups, and drum fills.

Args: unit_index: Audio unit index track_index: Note track index pitch: MIDI pitch for all ratchet notes (0-127) start_beat: Start position in beats length_beats: Total length in beats subdivisions: Subdivision mode — "accelerate" = start slow, get faster (16th→32nd→64th) "decelerate" = start fast, get slower (64th→32nd→16th) "constant" = even subdivision (no change, like a roll) "exponential" = exponential acceleration max_subdivisions: Maximum notes per beat at the fastest point (4=16th, 8=32nd, 16=64th, 32=128th) velocity: Base velocity (0-1) velocity_decay: Velocity reduction per note (0=uniform, 0.02=gradual fade) pitch_drift: Semitones to drift per note (0=same pitch, 1=ascending chromatic, -1=descending, 12=ascending octaves) region_index: Target region (-1 = auto-create/append)

Returns: JSON with notes_created, pitch, subdivision_points, total_beats.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
pitchNo
velocityNo
start_beatNo
unit_indexYes
pitch_driftNo
track_indexYes
length_beatsNo
region_indexNo
subdivisionsNoaccelerate
velocity_decayNo
max_subdivisionsNo

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes
Behavior4/5

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

With no annotations provided, the description carries the full burden. It clearly explains the behavioral effect (repeated notes with changing rate), defines subdivision modes, and describes parameters like velocity_decay and pitch_drift. It lacks explicit pre-conditions (e.g., track existence) but is otherwise transparent.

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

Conciseness4/5

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

The description is well-structured with a concise definition followed by a clear parameter breakdown. It is not overly verbose, but the musical context paragraph could be slightly trimmed. Still, every sentence adds value.

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?

Given the tool's complexity (11 parameters, no annotations), the description covers purpose, all parameters, and return value via output schema mention. It lacks error handling or prerequisites, but is generally complete for a creation tool.

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

Parameters5/5

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

The schema has 0% description coverage, but the description compensates with a detailed 'Args' section explaining every parameter's meaning, defaults, and allowed values (e.g., subdivisions modes, max_subdivisions mapping). This adds significant value beyond the schema's titles and defaults.

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 tool creates a ratchet, defines it as repeated notes with changing subdivision rate, and provides musical context. It distinguishes from sibling tools like create_trap_rolls or create_stutter by focusing on gradual acceleration/deceleration patterns.

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?

The description implies usage for accelerating or decelerating note sequences in Baroque, electronic, or drum fill contexts. However, it does not explicitly state when to use this tool over alternatives (e.g., create_stutter, create_buildup), nor does it provide when-not scenarios.

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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