lld— agent skill

Generate a Low Level Design (LLD) document from a freeform description and write it to a markdown file.

$ARGUMENTS may be:

• A freeform description of the feature, component, or system, or
• --hld <path> followed by an optional extra description (e.g. /lld --hld design/hld-user-auth.md focus on the token refresh flow). When --hld is provided, read the file at <path> and use its content as the primary source of context. The extra description, if present, narrows the scope.

If $ARGUMENTS is empty, ask the user to provide a description or an HLD path and stop.

Steps:

1. Parse $ARGUMENTS. If --hld <path> is present, read the file at <path>. Use the HLD content (plus any extra description) as the source for all sections below. If the path does not exist, tell the user and stop. If no --hld flag is present, use $ARGUMENTS as the description directly.

1. Derive a filename slug from the description or HLD title: lowercase, replace spaces and special characters with hyphens, truncate to ~5 words, and prefix with lld- (e.g. /lld user auth service → lld-user-auth-service.md).

1. Generate the LLD document with the following sections. Populate every section from the available context. If a section cannot be inferred, include it as a stub with a short prompt in italics (e.g. _TODO: list the error codes this endpoint returns._). If an HLD was provided, add a link to it in the Overview section.

Output structure:

• # LLD: <title derived from the description or HLD>
• **Date:** <today's date in YYYY-MM-DD format>
• **Status:** Draft
• **Author:** <!-- your name -->
• ## Overview — 2-3 sentences describing what this component does at the implementation level. If an HLD was provided, include a line: **HLD:** [<hld title>](<relative path to hld file>).
• ## Scope — what is covered in this document. List the specific classes, modules, endpoints, or functions in scope.
• ## API / Interface Design — the public interface: function signatures, REST endpoints, event schemas, or method contracts. Use code blocks where appropriate.
• ## Data Models — the data structures in use: fields, types, constraints, and relationships. Use tables or code blocks.
• ## Component Interactions — how this component calls and is called by others. Include sequence steps or a numbered interaction flow.
• ## Error Handling — what can go wrong, how errors are detected, and how they are surfaced to callers or users.
• ## Edge Cases — non-obvious inputs or states that require special handling.
• ## Testing Considerations — what unit, integration, or contract tests are needed. List the key scenarios to cover.
• ## Open Questions — unchecked checkboxes for implementation decisions that need to be resolved before coding begins.

1. Create a design/ directory in the current working directory if it does not already exist. Write the document to design/<slug>.md.

1. Tell the user the file path (design/<slug>.md) and confirm it was written. List any sections that were left as stubs.

Rules:

• Be specific — do not write generic filler. Every sentence must be grounded in the description or HLD content provided.
• The output must be ready to share or commit with no editing required, except for the stub sections.
• Do not add sections not listed above.

$ARGUMENTS