PostFader V12 — FL Studio MCP Server

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session_set_write_mode

DestructiveIdempotent

Enable or disable project write access for this FL Studio bridge session without restarting FL. Required before setters can change the project; turn it off when edits finish.

Instructions

Turn write mode on or off for this bridge session without restarting FL.

Setters (mixer_set_track, channel_set, plugin_set_parameter and the other
tools that change the project directly) refuse until write mode is on.
run_execute, run_continue, processing_apply, sound_apply_palette, and
review_apply_revision enable it for their own work. Enabling requires
confirm_user_present=true; the user's request to edit is that confirmation,
so do not ask separately. The result is verified with a fresh handshake.
Changes no project value, applies only to this session, and is never
saved. Disable it when the task's edits are done.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`enabled`	Yes	Absolute session write state. True unlocks the verified setters; false locks them again.
`confirm_user_present`	No	True asserts that the user asked for project changes in this task. Required to enable; not needed to disable.

Output Schema

TableJSON Schema

Name	Required	Default
`changed`	Yes
`verified`	No
`warnings`	No
`changed_at`	Yes
`bridge_mode`	Yes
`session_only`	No
`after_enabled`	Yes
`project_saved`	No
`before_enabled`	Yes
`bridge_command`	No	session.set_write_mode
`schema_version`	No	1.0
`requested_enabled`	Yes
`write_mode_origin`	Yes
`verification_basis`	No	post_transition_bridge_handshake
`session_fingerprint`	Yes
`confirmation_applied`	Yes
`confirmation_required`	Yes
`startup_default_enabled`	Yes
`runtime_write_mode_control`	No
`session_precondition_applied`	No

Schema Changelog

Changes observed during successful MCP inspections.

Addedv11.0.2Oct 5, 2026

TDQS

A4.9/5.0

Behavior5/5

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

Annotations cover the coarse profile (not read-only, idempotent, open-world, destructive), but the description adds real behavioral context the schema cannot: the refusal semantics of dependent setters, the confirmation-without-prompting rule, verification via a fresh handshake, and the explicit scope statement that it changes no project value, applies only to this session, and is never saved. This resolves the apparent tension with destructiveHint=true by clarifying that the risk is in what it unlocks, not in the call itself.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the core action in the first sentence, then layered preconditions and cleanup guidance. Every sentence carries distinct operational information; nothing restates the name or the schema.

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?

With an output schema present, return values need not be described. For a stateful session gate with two parameters, the description supplies everything an agent needs: precondition (confirm_user_present), scope (session-only, unsaved), interaction model (setters blocked until enabled), and lifecycle guidance (disable when done).

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

Parameters4/5

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

Schema description coverage is 100%, so the baseline is 3. The description goes beyond the schema by framing confirm_user_present interpretively ('the user's request to edit is that confirmation') and clarifying the asymmetry between enabling and disabling, which the schema only states mechanically.

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+resource+scope: toggling write mode for the current bridge session, explicitly 'without restarting FL'. It also distinguishes itself from the sibling setters it governs by naming mixer_set_track, channel_set and plugin_set_parameter, so an agent can place it correctly in the tool graph.

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?

Explicit about when it is needed (setters refuse until it is on), when it is NOT needed (run_execute, run_continue, processing_apply, sound_apply_palette, review_apply_revision enable it themselves), and when to turn it off ('Disable it when the task's edits are done'). The confirm_user_present precondition is spelled out with the routing instruction 'do not ask separately'.

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

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