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create_chord_progression

Insert a chord progression as voiced MIDI notes in REAPER. Parse chords like Cm7, Fm7, Bb7, set base octave, duration, and start position to place non-overlapping MIDI items.

Instructions

Insert a chord progression as voiced MIDI notes.

Accepts chords separated by commas, pipes, dashes, or newlines: "Cm7, Fm7, Bb7, Eb" or "Am - F - C - G" or "Dm | G | Em | A".

Supported qualities: maj, m/min, dim, dim7, aug, sus2, sus4, 6, m6, 7, m7, maj7, add9, 9, m9, maj9, 11, m11, 13, m13.

base_octave=4 places C as MIDI 60 (middle C). Each chord occupies chord_duration_qn quarter notes (default 4 QN = one bar at 4/4).

Pass item_index=-1 to auto-create a MIDI item positioned in the project at start_qn (e.g. bar 5 in 4/4 = start_qn=16.0). Building a multi-section arrangement on one track? Call this once per section with item_index=-1 each time and increasing start_qn — each call creates its own non-overlapping item at the right place, it does NOT append to a previous item.

Returns the item index, number of chords placed, and any that failed to parse.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
chordsYes
channelNo
start_qnNo
velocityNo
item_indexNo
base_octaveNo
track_indexYes
chord_duration_qnNo
Behavior5/5

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

With no annotations, the description fully discloses behavior: it creates non-overlapping items, does not append to previous ones, and returns the item index, number of chords, and failures. The note about auto-creating items and section placement is 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 purpose statement, followed by examples and clarifications. It is slightly lengthy but each sentence adds value; the front-loading is effective.

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

Completeness5/5

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

Given the 0% schema coverage and 8 parameters, the description is remarkably complete. It addresses return values, multi-section workflow, chord quality list, and default behaviors, leaving minimal gaps for the agent.

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

Parameters4/5

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

Schema coverage is 0%, but the description explains chords format, base_octave, chord_duration_qn, start_qn, and item_index in detail. It does not explain channel or velocity, but these are less critical defaults. Overall, it adds significant meaning beyond the schema.

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 'Insert a chord progression as voiced MIDI notes' with a specific verb and resource. It distinguishes itself from siblings like midi_insert_note by focusing on chord progressions with voicing and multiple delimiters.

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

Usage Guidelines4/5

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

The description provides explicit usage: acceptable chord delimiters, default values for duration and octave, and how to use item_index and start_qn for multi-section arrangements. It does not explicitly list when not to use, but the context is clear enough.

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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