PostFader V12 — FL Studio MCP Server

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piano_roll_write_notes

Destructive

Write notes into one channel's Piano Roll score in a pattern, using beat-based pitch, start, duration and velocity values. Use it to compose or replace MIDI notes in FL Studio.

Instructions

Write notes into one channel's Piano Roll score in a pattern.

Requires write mode and the one-time piano_roll_setup. Writes a local
script, selects the channel and pattern, and triggers FL's run-last-script
shortcut, then checks the selected target, the script's application, and
persistence. A dispatch alone is not proof the notes landed: inspect the
returned evidence, and treat a missing receipt as an unknown outcome, not a
reason to retry. Use piano_roll_transform_notes to edit existing notes.
Does not save the project.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`mode`	No	append keeps existing notes; replace clears the score first.	append
`notes`	Yes	Notes with pitch, start and duration in quarter-note beats, and velocity.
`auto_trigger`	No	Select the target and run the script automatically; false leaves both to the user.
`channel_index`	Yes	Global Channel Rack index from channel_list.
`pattern_number`	Yes	Pattern whose score to open; selected before the script runs.

Output Schema

TableJSON Schema

Name	Required	Default
`mode`	No
`status`	Yes
`target`	No
`trigger`	No
`warnings`	No
`operation`	Yes
`request_id`	Yes
`script_path`	Yes
`requested_at`	Yes
`project_saved`	No
`script_sha256`	Yes
`schema_version`	No	1.0
`verification_target`	No
`application_verified`	No
`requested_note_count`	No
`verification_trigger`	No
`requested_note_digest`	No
`script_runtime_evidence`	No
`verification_script_sha256`	No
`authoritative_note_readback_available`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed66 schema fields changedv11.0.2Oct 5, 2026
- changedInput schema / properties / auto_trigger / description
```
Previous value: -"Send FL's run-last-Piano-Roll-script shortcut after verified target selection."New value: +"Select the target and run the script automatically; false leaves both to the user."
```
- changedInput schema / properties / channel_index / description
```
Previous value: -"Global Channel Rack target index."New value: +"Global Channel Rack index from channel_list."
```
- changedInput schema / properties / mode / description
```
Previous value: -"Append to the score or clear all notes before adding these notes."New value: +"append keeps existing notes; replace clears the score first."
```
- changedInput schema / properties / notes / description
```
Previous value: -"Bounded notes in quarter-note beat units."New value: +"Notes with pitch, start and duration in quarter-note beats, and velocity."
```
- changedInput schema / properties / pattern_number / description
```
Previous value: -"Pattern to select before triggering the script."New value: +"Pattern whose score to open; selected before the script runs."
```
- removedOutput schema / $defs / HotkeyDispatch / properties / error / title
```
Removed value: -"Error"
```
- removedOutput schema / $defs / HotkeyDispatch / properties / fl_window_focused / title
```
Removed value: -"Fl Window Focused"
```
- removedOutput schema / $defs / HotkeyDispatch / properties / fl_window_found / title
```
Removed value: -"Fl Window Found"
```
- removedOutput schema / $defs / HotkeyDispatch / properties / hotkey_dispatched / title
```
Removed value: -"Hotkey Dispatched"
```
- removedOutput schema / $defs / HotkeyDispatch / properties / platform / title
```
Removed value: -"Platform"
```
- removedOutput schema / $defs / HotkeyDispatch / properties / shortcut / title
```
Removed value: -"Shortcut"
```
- removedOutput schema / $defs / HotkeyDispatch / title
```
Removed value: -"HotkeyDispatch"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / properties / added_note_digest_sha256 / title
```
Removed value: -"Added Note Digest Sha256"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / properties / before_note_count / title
```
Removed value: -"Before Note Count"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / properties / error / title
```
Removed value: -"Error"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / properties / evidence_scope / title
```
Removed value: -"Evidence Scope"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / properties / expected_added_note_count / title
```
Removed value: -"Expected Added Note Count"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / properties / mode / title
```
Removed value: -"Mode"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / properties / operation / title
```
Removed value: -"Operation"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / properties / persistence_check_completed / title
```
Removed value: -"Persistence Check Completed"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / properties / persistence_check_verified / title
```
Removed value: -"Persistence Check Verified"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / properties / postcondition_verified / title
```
Removed value: -"Postcondition Verified"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / properties / ppq / title
```
Removed value: -"Ppq"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / properties / receipt_authentication_verified / title
```
Removed value: -"Receipt Authentication Verified"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / properties / receipt_path / title
```
Removed value: -"Receipt Path"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / properties / receipt_sha256 / title
```
Removed value: -"Receipt Sha256"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / properties / request_id / title
```
Removed value: -"Request Id"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / properties / requested_note_digest / title
```
Removed value: -"Requested Note Digest"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / properties / score_digest_sha256 / title
```
Removed value: -"Score Digest Sha256"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / properties / score_note_count / title
```
Removed value: -"Score Note Count"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / properties / script_completed / title
```
Removed value: -"Script Completed"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / properties / verification_receipt_path / title
```
Removed value: -"Verification Receipt Path"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / properties / verification_receipt_sha256 / title
```
Removed value: -"Verification Receipt Sha256"
```
- removedOutput schema / $defs / PianoRollScriptRuntimeEvidence / title
```
Removed value: -"PianoRollScriptRuntimeEvidence"
```
- removedOutput schema / $defs / PianoRollTargetReceipt / properties / after_channel_indices / title
```
Removed value: -"After Channel Indices"
```
- removedOutput schema / $defs / PianoRollTargetReceipt / properties / after_pattern_number / title
```
Removed value: -"After Pattern Number"
```
- removedOutput schema / $defs / PianoRollTargetReceipt / properties / before_channel_indices / title
```
Removed value: -"Before Channel Indices"
```
- removedOutput schema / $defs / PianoRollTargetReceipt / properties / before_pattern_number / title
```
Removed value: -"Before Pattern Number"
```
- removedOutput schema / $defs / PianoRollTargetReceipt / properties / channel_index / title
```
Removed value: -"Channel Index"
```
- removedOutput schema / $defs / PianoRollTargetReceipt / properties / command / title
```
Removed value: -"Command"
```
- removedOutput schema / $defs / PianoRollTargetReceipt / properties / pattern_number / title
```
Removed value: -"Pattern Number"
```
- removedOutput schema / $defs / PianoRollTargetReceipt / properties / piano_roll_visibility_verified / title
```
Removed value: -"Piano Roll Visibility Verified"
```
- removedOutput schema / $defs / PianoRollTargetReceipt / properties / piano_roll_visible_after / title
```
Removed value: -"Piano Roll Visible After"
```
- removedOutput schema / $defs / PianoRollTargetReceipt / properties / piano_roll_visible_before / title
```
Removed value: -"Piano Roll Visible Before"
```
- removedOutput schema / $defs / PianoRollTargetReceipt / properties / project_saved / title
```
Removed value: -"Project Saved"
```
- removedOutput schema / $defs / PianoRollTargetReceipt / properties / selected_target_verified / title
```
Removed value: -"Selected Target Verified"
```
- removedOutput schema / $defs / PianoRollTargetReceipt / properties / session_fingerprint / title
```
Removed value: -"Session Fingerprint"
```
- removedOutput schema / $defs / PianoRollTargetReceipt / properties / session_precondition_applied / title
```
Removed value: -"Session Precondition Applied"
```
- removedOutput schema / $defs / PianoRollTargetReceipt / properties / target_fingerprint / title
```
Removed value: -"Target Fingerprint"
```
- removedOutput schema / $defs / PianoRollTargetReceipt / title
```
Removed value: -"PianoRollTargetReceipt"
```
- removedOutput schema / properties / application_verified / title
```
Removed value: -"Application Verified"
```
- removedOutput schema / properties / authoritative_note_readback_available / title
```
Removed value: -"Authoritative Note Readback Available"
```
- removedOutput schema / properties / mode / title
```
Removed value: -"Mode"
```
- removedOutput schema / properties / operation / title
```
Removed value: -"Operation"
```
- removedOutput schema / properties / project_saved / title
```
Removed value: -"Project Saved"
```
- removedOutput schema / properties / request_id / title
```
Removed value: -"Request Id"
```
- removedOutput schema / properties / requested_at / title
```
Removed value: -"Requested At"
```
- removedOutput schema / properties / requested_note_count / title
```
Removed value: -"Requested Note Count"
```
- removedOutput schema / properties / requested_note_digest / title
```
Removed value: -"Requested Note Digest"
```
- removedOutput schema / properties / schema_version / title
```
Removed value: -"Schema Version"
```
- removedOutput schema / properties / script_path / title
```
Removed value: -"Script Path"
```
- removedOutput schema / properties / script_sha256 / title
```
Removed value: -"Script Sha256"
```
- removedOutput schema / properties / status / title
```
Removed value: -"Status"
```
- removedOutput schema / properties / verification_script_sha256 / title
```
Removed value: -"Verification Script Sha256"
```
- removedOutput schema / properties / warnings / title
```
Removed value: -"Warnings"
```
- removedOutput schema / title
```
Removed value: -"PianoRollDispatch"
```
Changed19 schema fields changedv11.0.1Oct 3, 2026
- removedInput schema / $defs / CreativeNote / properties / color / title
```
Removed value: -"Color"
```
- removedInput schema / $defs / CreativeNote / properties / duration_beats / title
```
Removed value: -"Duration Beats"
```
- removedInput schema / $defs / CreativeNote / properties / muted / title
```
Removed value: -"Muted"
```
- removedInput schema / $defs / CreativeNote / properties / pan / title
```
Removed value: -"Pan"
```
- removedInput schema / $defs / CreativeNote / properties / pitch / title
```
Removed value: -"Pitch"
```
- removedInput schema / $defs / CreativeNote / properties / pitch_offset_tenths / title
```
Removed value: -"Pitch Offset Tenths"
```
- removedInput schema / $defs / CreativeNote / properties / portamento / title
```
Removed value: -"Portamento"
```
- removedInput schema / $defs / CreativeNote / properties / release / title
```
Removed value: -"Release"
```
- removedInput schema / $defs / CreativeNote / properties / selected / title
```
Removed value: -"Selected"
```
- removedInput schema / $defs / CreativeNote / properties / slide / title
```
Removed value: -"Slide"
```
- removedInput schema / $defs / CreativeNote / properties / start_beats / title
```
Removed value: -"Start Beats"
```
- removedInput schema / $defs / CreativeNote / properties / velocity / title
```
Removed value: -"Velocity"
```
- removedInput schema / $defs / CreativeNote / title
```
Removed value: -"CreativeNote"
```
- removedInput schema / properties / auto_trigger / title
```
Removed value: -"Auto Trigger"
```
- removedInput schema / properties / channel_index / title
```
Removed value: -"Channel Index"
```
- removedInput schema / properties / mode / title
```
Removed value: -"Mode"
```
- removedInput schema / properties / notes / title
```
Removed value: -"Notes"
```
- removedInput schema / properties / pattern_number / title
```
Removed value: -"Pattern Number"
```
- removedInput schema / title
```
Removed value: -"piano_roll_write_notesArguments"
```
First observedv10.0.0Sep 14, 2026

TDQS

A4.6/5.0

Behavior5/5

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

Goes well beyond the annotations: it discloses the mechanism (writes a local script, selects channel/pattern, triggers FL's run-last-script shortcut), the post-run verification checks, and critically warns that a dispatch is not proof of success and that a missing receipt is an unknown outcome rather than a retry signal. That retry guidance is exactly the kind of behavior an agent cannot infer from destructiveHint=false/idempotentHint=false.

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-loaded with the action, then prerequisites, then verification guidance in descending priority. Dense but every sentence carries information; only the verification paragraph is slightly verbose relative to the core instruction.

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?

An output schema exists so return values need not be explained, and the annotations carry the safety profile. What the description does add — write-mode requirement, setup dependency, non-persistence, and how to interpret the returned evidence — closes the remaining gaps for a destructive, non-idempotent write tool.

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%, so the schema already documents notes, mode, auto_trigger, channel_index and pattern_number. The description adds only indirect context (channel/pattern selection, local script write) and never explains the append vs replace distinction, so 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 (Write), resource (notes), and precise scope (one channel's Piano Roll score in a pattern). It explicitly separates itself from piano_roll_transform_notes, 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.

Usage Guidelines5/5

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

Gives prerequisites (requires write mode and the one-time piano_roll_setup), the alternative for editing (piano_roll_transform_notes), and a boundary condition (does not save the project). Both the when-to-use and the when-to-use-something-else are stated.

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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