Select items on a REAPER track by index range, or select all items when start and end are -1. Set replace to clear other selections first.
Select items on a track by index range. Pass start=-1, end=-1 to select all items on the track. replace = clear other selections first.
| Name | Required | Description | Default |
|---|---|---|---|
| replace | No | ||
| end_item | No | ||
| start_item | No | ||
| track_index | Yes |
Changes observed during successful MCP inspections.
v0.2.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden, and it does disclose two meaningful behaviors: the -1 sentinel meaning 'all items' and that `replace` clears prior selections. It omits error behavior for invalid track indices, whether the selection persists across other calls, and the indexing base.
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?
Three short sentences with zero filler, front-loading the core action before the sentinel and replace details. Every sentence earns its place.
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 4-param, no-annotation, no-output-schema mutation-of-selection tool, the description covers the headline action but leaves indexing conventions and failure behavior unaddressed. Adequate but with clear gaps.
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, and it explains start_item/end_item sentinels and the replace flag. However, it never clarifies whether track_index/start_item/end_item are zero-based, which is critical for a selection tool, leaving the required parameter partly ambiguous.
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 and resource (select items on a track) and scopes it to an index range, which distinguishes it from the track-level select_tracks sibling. It does not explicitly name a sibling or alternative, so it falls short of the top tier.
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?
It explains the -1/-1 shortcut for selecting everything and what `replace` does, which implies usage, but gives no when-to-use vs alternatives, no prerequisites, and no indication of what happens after selection. Usage context must be inferred.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.