PostFader V12 — FL Studio MCP Server

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pattern_create

Destructive

Creates an FL Studio pattern by finding the first empty slot, selecting it, then setting its name, length, and optional color with step-by-step verification.

Instructions

Create a pattern: find the first empty one, select it, name it, and size it.

Requires write mode. Searches from start_pattern_number for a pattern FL
reports as empty, then selects it and sets its name, optional color, and
length, verifying each step. outcome names the first step that did not
verify. Use pattern_set to change an existing pattern. Does not save.

Input Schema

TableJSON Schema

Name	Required	Description
`name`	Yes	Name for the new pattern.
`color`	No	Optional FL color word.
`length_beats`	No	Pattern length in beats.
`start_pattern_number`	No	First pattern number to search for an empty one.

Output Schema

TableJSON Schema

Name	Required	Default
`length`	No
`outcome`	Yes
`identity`	No
`verified`	Yes
`warnings`	No
`selection`	Yes
`applied_at`	Yes
`project_saved`	No
`pattern_number`	Yes
`schema_version`	No	1.0
`one_session_target`	Yes
`rollback_attempted`	No
`automatic_replay_attempted`	No
`pattern_was_reported_empty`	No

Schema Changelog

Changes observed during successful MCP inspections.

Addedv11.0.2Oct 5, 2026

TDQS

A4.7/5.0

Behavior5/5

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

Adds substantial behavior beyond the annotations: it discloses the write-mode authorization requirement, that the target slot is chosen by searching from start_pattern_number for a slot FL reports as empty (so existing patterns are not overwritten), that each step is verified with an 'outcome' field naming the first unverified step, and that the result is not persisted ('Does not save'). None of this is derivable from destructiveHint/idempotentHint alone.

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 verb and a one-line summary, followed by the precise operational detail and the alternative-tool pointer. Every sentence carries new information; the short summary-plus-detail structure aids scanning without padding.

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 preconditions, side-effect scope, verification semantics, persistence behavior, and the sibling alternative. With an output schema present and 100% schema coverage, no essential information is missing for correct invocation.

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 already 100%, so the baseline is 3, but the description adds operational meaning: start_pattern_number defines the search origin for the first empty slot, and name/color/length map to the name-select-size sequence performed on that slot. It does not add syntax or format detail beyond the schema, so it stays just above baseline.

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 ('Create a pattern') and then enumerates the exact sub-steps (find first empty, select, name, size). It explicitly distinguishes itself from the sibling 'pattern_set', which handles modification of existing patterns, 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 Guidelines4/5

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

Gives a real precondition ('Requires write mode') and names the alternative for the adjacent case ('Use pattern_set to change an existing pattern'). It does not spell out when creating a fresh pattern is the right move versus higher-level compose_* or piano_roll_* helpers, but the context is clear enough to select the tool.

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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