Creates a return bus for effects like reverb or delay, enabling shared effect routing from tracks via sends and returning the updated mixer.
Add a return bus (e.g. 'Reverb', 'Delay'): put an effect on it with devices.add ({"return_bus": n}, usually at 100% mix) and feed it from tracks with mixer.set_send. Returns the mixer. Undoable.
| Name | Required | Description | Default |
|---|---|---|---|
| name | No | Name (default 'Return N'). |
Changes observed during successful MCP inspections.
v0.3.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations cover read-only/destructive/idempotent, but the description adds two traits they do not: the call returns the mixer (important since there is no output schema) and the operation is undoable. It leaves open whether duplicate names create a second bus or collide, which is the one meaningful gap.
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?
One dense sentence that front-loads what is created, then the follow-up steps, then the return value and undoability. No filler and nothing repeated from the schema.
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-optional-parameter creation tool with no output schema, the description supplies the return value, undoability, naming convention, and the two follow-up calls needed to make the bus useful. Nothing an agent needs in order to invoke it correctly is missing.
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 100% and already documents the default ('Return N'), so the baseline is 3. The description adds real meaning by showing the naming convention in practice (name the bus after the effect, e.g. 'Reverb', 'Delay'), which guides an agent beyond the raw type declaration.
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 and resource ("Add a return bus") with concrete examples of what a return bus is used for ('Reverb', 'Delay'). The inverse sibling mixer_remove_return makes the add/remove pair obvious, so an agent can route correctly without opening either schema.
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?
Gives the full workflow that follows creation: attach an effect via devices.add with {"return_bus": n} at ~100% mix, then feed it with mixer.set_send. That names the alternative/adjacent tools and the ordering, though it does not state when not to create a return bus (e.g. reusing an existing one via mixer_get/mixer_set_return).
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.