PostFader V12 — FL Studio MCP Server

Overview Schema Source Related Servers Discussions Admin

mixer_start_peak_watch

Start background sampling of FL Studio mixer peak meters during playback to measure post-fader levels for gain staging, then read or stop the watch.

Instructions

Start sampling mixer peak meters while the user plays the song.

Runs in the background in this MCP process and returns its first frame and
a watch_id. Ask the user to play the section to measure, then read it with
mixer_get_peak_watch or end it with mixer_stop_peak_watch. Changes no
project state. Meter peaks are post-fader samples, not audio analysis; use
the watch with mixer_plan_gain_staging to propose fader moves.

Input Schema

TableJSON Schema

Name	Required	Description
`only_used`	No	Keep only active or custom-named tracks plus Master.
`max_tracks`	No	Maximum mixer indices scanned per sample.
`interval_ms`	No	Sampling interval in milliseconds.
`duration_seconds`	No	How long to sample.

Output Schema

TableJSON Schema

Name	Required	Default
`error`	No
`status`	Yes
`tracks`	Yes
`watch_id`	Yes
`only_used`	Yes
`max_tracks`	Yes
`started_at`	Yes
`finished_at`	No
`frame_count`	Yes
`interval_ms`	Yes
`limitations`	No
`schema_version`	No	1.0
`session_fingerprint`	No
`requested_duration_seconds`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Addedv11.0.2Oct 5, 2026

TDQS

A4.4/5.0

Behavior4/5

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

Annotations cover the safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=true, idempotentHint=false), and the description adds meaningful context beyond them: it runs in the background in this MCP process, returns a first frame and watch_id, changes no project state, and that peaks are post-fader samples rather than audio analysis. It does not note the non-idempotent/non-repeatable nature or the interaction of concurrent watches, so it stops short of a 5.

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?

Front-loads the action and its trigger, then the lifecycle and the semantic caveat. Every sentence is load-bearing, though the last sentence is dense with three distinct claims packed together.

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?

Covers the full lifecycle (start, read, stop), the return value despite an output schema existing, the no-side-effect guarantee, and the semantic caveat that peaks are post-fader samples. An agent has everything needed to invoke and follow up correctly.

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 defaults and ranges on all four parameters, so the schema carries parameter meaning. The description adds no parameter-specific guidance (e.g. how duration_seconds or interval_ms interact with sampling fidelity), so the baseline 3 applies.

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?

States a specific verb and resource ('Start sampling mixer peak meters') plus the operational context ('while the user plays the song'). It also names the sibling tools it pairs with (mixer_get_peak_watch, mixer_stop_peak_watch, mixer_plan_gain_staging), so it is clearly distinguishable from them.

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?

Gives an explicit workflow: start the watch, ask the user to play the section, then read with mixer_get_peak_watch or end with mixer_stop_peak_watch. It also specifies the downstream use case (mixer_plan_gain_staging to propose fader moves), which routes the agent correctly.

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

Deploy Server