Control the stereo panning of a track in REAPER. Set pan from -1.0 (left) through 0 (center) to 1.0 (right).
Set the pan position of a track.
Args: pan: Pan position from -1.0 (full left) to 1.0 (full right). 0 = center.
| Name | Required | Description | Default |
|---|---|---|---|
| pan | Yes | ||
| track_index | Yes |
Changes observed during successful MCP inspections.
v1.7.3Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full behavioral burden. It discloses the valid input range, but says nothing about whether the change is persistent, whether it is undoable, whether the track must be selected or armed first, or what happens on out-of-range values.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is short and front-loaded: the operation comes first, then the argument semantics. The Args block is slightly formulaic but wastes no words.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a simple two-parameter setter with no annotations and no output schema, the description is adequate on pan but incomplete on track_index and silent on side effects. It is minimally viable rather than complete.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 0%, so the description must compensate. It fully documents the pan parameter's range and center value, which is genuinely useful, but leaves track_index entirely unexplained, including whether indexing is 0- or 1-based, which is a real ambiguity for a positional setter.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description states a specific verb (Set) and resource (pan position of a track), which is clear and unambiguous. It does not name or contrast itself with siblings like set_track_volume or set_track_phase, but the operation itself is unmistakable.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
There is no guidance on when to use this tool versus alternatives, no prerequisites (e.g., that track_index must refer to an existing track), and no statement about required permissions or context. Usage has to be inferred entirely from the name.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.