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name: setup-custom-libraries description: Register, add, or update existing custom Simulink block libraries and configure block policy and knowledge index. Use when a user wants to register, set up, configure, or add existing .slx library files for agent-assisted model building. Do NOT use when the user wants to create or author a new library from scratch — that requires building-simulink-models. license: https://www.mathworks.com/content/dam/mathworks/license/pmrl/license.md metadata: author: MathWorks version: "1.2"

Setup Custom Libraries

Register or update custom Simulink block libraries so the agent prefers them over built-in blocks during model building.

When to Use

• User asks to set up, register, add, or configure custom libraries
• User wants to add new .slx files to an existing library configuration
• User says "setup custom libraries", "add my library", "configure libraries", "add a new library file"
• building-simulink-models routes here via the policy gate (gatePass: false)
• Never invoke when found: false — that means no custom libraries are configured and the user hasn't asked for them

When NOT to Use

• User wants to create a custom library from scratch (author new blocks, build a new .slx library file) → use building-simulink-models skill with model_edit directly. This skill only registers existing libraries; it cannot create library content.
• Only configuring block exclusions or parameter protection (libraries already declared) → configuring-block-policy
• Only curating block descriptions/categories (libraries already declared) → simulink-curating-library-kg

Workflow

Do this FIRST and ALONE — no other tool calls in the same message.

Call library.settingsLookup() — returns a struct with resolved absolute paths:

• found — whether a libraries file was located (satk-libraries.json or legacy reuse-libraries.json)
• enabled — whether custom libraries are configured
• gatePass — whether the gate is satisfied
• dataRoot — absolute path to the directory containing .satk/
• kgIndexPath, librariesPath, policyPath — absolute paths to data files

Interpret the result:

• found: false → no custom libraries configured. Do NOT proceed with setup unless the user explicitly asked. Return control to the calling skill.
• gatePass: true, found: true → all data files present and KB populated. Offer management menu (below).
• gatePass: false, found: true → libraries declared but KB needs population. Skip Gate 1 (libraries already exist). Start from Gate 2 below using dataRoot as the target.

Follow references/library-setup.md for all gate API details — it is the single source of truth for API calls, examples, and options at each gate.

Gate 1 — Library declaration: Only when the user explicitly asked to set up custom libraries and no libraries file exists yet. STOP and ask the user about reusable libraries. Present two options: Yes (declare libraries) or None (no libraries right now). Do not read reference files, open models, or plan blocks until they respond.

• If user provides libraries (Yes) → save to prefdir via library.LibraryConfig.save(prefdir(), libraries).
• If user says "none" → do not create any files. The gate remains open (no config = use standard blocks).

Gate 2 — Block policy: If .satk/block-policy.json is missing, STOP and ask the user about policy setup by following references/library-setup.md. Do not proceed until policy is resolved.

Gate 3 — Library blocks knowledge index: If the KB is empty (index.md contains populated: false) or missing, STOP and ask the user whether to index their library blocks so the agent knows which blocks are available during model building. Offer two options: Automatic (agent infers categories/descriptions autonomously) or Guided setup (interactive curation). Both invoke the simulink-curating-library-kg skill. Follow references/library-setup.md for details. Do not proceed until KG generation completes.

Management menu (config already complete)

Retrieve and display the user's current configuration status using the APIs in references/library-setup.md § "Status Display (Management Menu)". Show library names/paths, policy mode with fallback, and KG block/category counts. Then offer:

• (a) Add or remove libraries — load existing config via library.LibraryConfig.load(dataRoot), append/remove entries, save via library.LibraryConfig.save(dataRoot, allLibs), then invoke simulink-curating-library-kg skill (automatic mode) to regenerate KG.
• (b) Update block policy — load configuring-block-policy skill.
• (c) Promote config to prefdir — only show if tier is project or legacy. Copy .satk/ folder to prefdir/.satk/ (expand relative paths to absolute). See references/library-setup.md § "Gate 1" for the promote API.
• (d) Regenerate knowledge index — load simulink-curating-library-kg skill.

Adding files to existing config

When satk-libraries.json already exists with declared libraries: read the existing config, append the new library entries, save via library.LibraryConfig.save(), then invoke the simulink-curating-library-kg skill (automatic mode) to infer categories/descriptions for the new blocks and regenerate the knowledge index.

Guardrails

• Never write config files or .satk/ JSON manually. Always follow the instructions and APIs in references/library-setup.md for each case.
• Do not use find_system, load_system to discover, validate, or enumerate library contents. All library operations must go through the specified APIs in references/library-setup.md.
• Each gate requires explicit user input before proceeding. Do not assume anything, wait for the response before moving to the next gate.
• Paths at prefdir must be absolute. (Project-level paths can be relative to project root.)

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Copyright 2026 The MathWorks, Inc.

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