PostFader V10 — FL Studio MCP Server

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fl_set_write_mode

DestructiveIdempotent

Toggle write access for the current FL Studio bridge session. Enable only when the user confirms presence; disable to lock write tools. Applies immediately without restarting.

Instructions

Enable or disable writes for this bridge session without restarting FL.

This changes no project value and never persists the setting. Enabling is
refused unless `confirm_user_present` is literally true. The result is
verified with a fresh bridge handshake before it reports success.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`enabled`	Yes	Absolute session write state. True exposes only the bounded verified write tools; false locks them again.
`confirm_user_present`	No	True asserts that the user requested project changes or write access in this task. No separate mode request is needed. Not required 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.

First observedv10.0.0Sep 14, 2026

TDQS

A4.4/5.0

Behavior4/5

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

Annotations provide readOnlyHint=false, destructiveHint=true, idempotentHint=true, but the description adds crucial context: it 'changes no project value and never persists the setting,' which clarifies that the tool is non-destructive itself and non-persistent. It also discloses the precondition for enabling (refused unless `confirm_user_present` is literally true) and that the result is verified with a fresh bridge handshake before success is reported. This goes beyond the annotations by explaining the verification and non-persistence aspects. No contradiction with annotations.

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?

The description is concise and well-structured. The first sentence states the primary purpose immediately, and subsequent sentences provide essential clarifications: no project value change, no persistence, the confirmation requirement, and the verification step. Every sentence adds value without redundancy. It is front-loaded and easy to scan.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The description covers the key operational aspects: what the tool does, its side effects (none on project values), its persistence (none), the precondition for enabling, and the verification mechanism. It does not explicitly describe the return value, but an output schema exists, so that is covered. It also does not elaborate on the exact effect of disabling, but the schema mentions 'false locks them again,' which covers that. Overall, it is complete for a mode-toggle tool with these annotations and schema.

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 coverage is 100%, so both parameters are well-documented in the schema. The description reinforces the meaning of `confirm_user_present` by stating that enabling is refused unless it is literally true, which adds practical context beyond the schema's description. It also clarifies the `enabled` parameter's effect via the phrase 'enable or disable writes.' Since the schema already covers the basics, the description adds a small but valuable semantic nuance.

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 clearly states the action: 'Enable or disable writes for this bridge session without restarting FL.' It specifies the resource (bridge session) and the action (enable/disable writes), and distinguishes itself from direct parameter-changing tools by noting it 'changes no project value.' This is a specific, unambiguous purpose that sets it apart from siblings like fl_set_mixer_volume.

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

Usage Guidelines4/5

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

The description implicitly communicates when to use this tool: it is a session-level mode toggle, not a direct project modification. It states 'This changes no project value,' which tells the agent this is not for direct edits, and it clarifies that enabling requires `confirm_user_present` to be true. While it does not explicitly say 'use this before performing write operations,' the context and the contrast with other fl_set_* tools make the usage clear enough. Lacks an explicit exclusion or alternative mention, but the purpose is self-evident.

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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