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yiw190

reaper-mcp

by yiw190
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Local

envelope

List, read, or set REAPER track automation points for Volume, Pan, Mute, and other parameters; set replaces all points, supports dB or gain units, and reactivates inactive lanes.

Instructions

Track envelopes. action: list | get | set. name is REAPER envelope name (Volume, Pan, Mute, ...). set replaces all points. value is the envelope's value; Volume is linear gain (1.0 = 0 dB, 0.5 = -6 dB), also on fader-scaled envelopes. unit=db reads/writes volume-type envelopes (Volume, Trim Volume, send Volume) in dB. set re-activates an envelope left inactive (ACT 0).

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
nameNo
unitNo
actionYes
pointsNo
track_indexYes
envelope_indexNo

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv0.5.0
    • addedInput schema / properties / unit
      Added value: +{
+  "enum": [
+    "gain",
+    "db"
+  ],
+  "type": "string"
+}
  2. First observedv0.1.0

TDQS

B3.1/5.0
Behavior3/5

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

With no annotations, the description carries the full behavioral burden. It does disclose important mutation semantics: set replaces all points and re-activates an inactive envelope. However, it omits other relevant behavior such as what list/get return, whether set requires the envelope to exist, and how track_index/envelope_index interact.

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 dense and front-loads the action modes, then moves into parameter-specific notes. It is appropriately sized, though the phrase 'value is the envelope's value' is tautological and the order of notes is somewhat ad hoc.

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

Completeness2/5

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

For a mutable 6-parameter tool with no annotations, no output schema, and no schema parameter descriptions, the description covers domain semantics well but leaves key gaps: track vs envelope indexing, list/get return behavior, and nested point fields. An agent could call set, but list/get usage remains under-specified.

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

Parameters2/5

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

Schema description coverage is 0%, so the description must explain all six parameters. It adds useful meaning for action, name, unit, value, and points, including gain/dB scaling, but never explains track_index (including the -1 minimum) or envelope_index, both of which are critical for locating the envelope.

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

Purpose4/5

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

The description identifies the resource as REAPER envelopes and names the three operations (list, get, set). 'Track envelopes' alone is slightly ambiguous as a verb, but the action enumeration makes the tool's purpose clear enough to distinguish it from siblings like item, fx, or send.

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 action modes and notes on unit=db and set behavior imply when each mode is appropriate, but there is no explicit guidance on choosing list vs get vs set, nor any statement of when to use this tool instead of sibling tools. Usage is inferable rather than spelled out.

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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