Set the Arrangement loop start in Ableton Live to a chosen beat; the change is verified by read-back in one undo step.
Set Arrangement loop start with read-back verification.
Side effects: writes loop geometry in one undo step.
Example: set_loop_start(16.0) starts the loop at beat sixteen.
Edge cases: a stuck setter raises PLAYHEAD_NOT_MOVED.
| Name | Required | Description | Default |
|---|---|---|---|
| start_beat | Yes |
Changes observed during successful MCP inspections.
v0.7.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden and does well: it discloses read-back verification, that the write occurs in a single undo step, and a concrete failure mode (PLAYHEAD_NOT_MOVED). It omits whether the operation is reversible beyond undo grouping and what the verification step returns.
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?
Four short, front-loaded sentences each carrying distinct information (purpose, side effect, example, edge case). No filler and the core action leads.
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 single-parameter mutation tool with no annotations and no output schema, this covers the essential behavioral surface: side effect, undo semantics, example, and error path. Only the read-back verification result and parameter bounds are left implicit.
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 coverage is 0% and the single parameter start_beat has no type description beyond 'number'. The example set_loop_start(16.0) starts the loop at beat sixteen supplies the missing unit and format, which for a lone numeric parameter is meaningful compensation, though valid ranges or bounds remain unspecified.
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?
States a specific verb+resource: sets the Arrangement loop start point. This distinguishes it reasonably from look-alikes such as set_loop_length (length) and get_loop_settings (read), though it does not explicitly disambiguate itself from set_loop, which may also touch loop start.
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?
The example implies usage context (Arrangement loop start at a given beat), but there is no explicit guidance on when to prefer this over set_loop or set_loop_length, nor any prerequisite or when-not-to-use statement. Usage is only implied.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.