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play

Idempotent

Start transport playback in Ableton Live and verify it is running by reading back the is_playing status. Optionally cue to a specific beat or resume from the current position.

Instructions

Start transport playback and read back the is_playing status.

Returns:
    Dictionary reporting the start call and the read-back is_playing flag.

Note:
    The read-back proves the transport is running, not that anything is audible:
    a muted track, an empty Arrangement or a track with no instrument all play
    silently. Use stop to halt, and set_arrangement_time to move the playhead
    without starting.

    Leave the transport as it was found. Nothing here stops it on its own, and a
    set left playing keeps playing for whoever is at the machine.

    A Session clip that has played leaves its track in Session view, and the
    track then ignores the Arrangement until Live's Back to Arrangement button
    is pressed. ``song.back_to_arranger`` reports that state and clears it
    when written false (applied asynchronously, taking up to 2 read-back
    attempts for ``read_back: "applied"``).

Input Schema

TableJSON Schema

Name	Required	Description	Default
`from_beat`	No	Cue the playhead to this beat before starting, in beats from the start of the Arrangement. Omit to start from wherever the playhead already sits.
`continue_playing`	No	True resumes from the current position instead of restarting. Ignored when from_beat is given, since that sets the position.

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedv0.1.1Sep 7, 2026

addedInput schema / properties / continue_playing / description

Added value: +"True resumes from the current position instead of restarting. Ignored when from_beat is given, since that sets the position."

addedInput schema / properties / from_beat / description

Added value: +"Cue the playhead to this beat before starting, in beats from the start of the Arrangement. Omit to start from wherever the playhead already sits."

First observedv0.1.0Sep 5, 2026

TDQS

A4.6/5.0

Behavior5/5

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

Annotations only provide high-level flags (not read-only, idempotent, not destructive). The description adds substantial behavioral context beyond those flags: the read-back proves transport running rather than audibility, the transport is left running, and Session clip playback can make a track ignore the Arrangement until Back to Arrangement is triggered.

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 longer than minimal, but it is front-loaded with the core purpose and then structured into useful blocks: return value, caveats, transport state, and Session/Arrangement behavior. Each block earns its place, though the last paragraph is detailed enough that a slightly tighter version would be possible.

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 tool's side effects and edge cases, the description is complete: it states the return dictionary, the non-audibility caveat, the leave-transport-as-found policy, the Session clip interaction, and the asynchronous back_to_arranger behavior. The full input schema and output schema cover the remaining structured details.

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

Parameters3/5

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

Schema description coverage is 100%, with both from_beat and continue_playing already explained in detail, including the interaction where from_beat overrides continue_playing. The tool description does not need to add parameter semantics, so the baseline of 3 is appropriate.

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 opens with a specific verb and resource: 'Start transport playback and read back the is_playing status.' It also names sibling tools stop and set_arrangement_time, so an agent can distinguish play from related transport operations without opening other definitions.

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

Usage Guidelines5/5

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

The description explicitly states when to use alternatives: 'Use stop to halt, and set_arrangement_time to move the playhead without starting.' It also clarifies that playback may be silent, which sets expectations for whether calling this tool is useful in a given context.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.