kicad-mcp-layer

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lib_fetch

Idempotent

Fetch symbol, footprint and 3D model files for an LCSC code into a KiCad library beside your project. Use them to draft a part swap, then verify pads against the datasheet.

Instructions

Symbol, footprint and 3D model (STEP and WRL) for one LCSC code, converted from EasyEDA's component data (EasyEDA is JLCPCB's own design tool; nearly every part in the assembly catalogue has a model there) by easyeda2kicad into a library next to the project. A part swap becomes: parts_search for the code and stock, lib_fetch for the files, then fp_info and the datasheet drawing (doc_page) for the pad-for-pad check. The models are drawn by users and JLCPCB staff: treat them as drafts, never as verified.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`lcsc`	Yes	LCSC code such as C520543, as parts_search or jlcpcb.com/parts give it.
`parts`	No		full
`lib_dir`	No	Folder for the library files instead of <project>/lib; must be inside the workspace.
`lib_name`	No	Library base name: <lib_name>.kicad_sym, <lib_name>.pretty and <lib_name>.3dshapes; several parts share one library.	jlc
`overwrite`	No	Replace a symbol, footprint or model of the same name already in the library.
`project_path`	No	The project (.kicad_pro or its folder) whose lib/ receives the files. Register <lib_name> in its sym-lib-table and fp-lib-table afterwards.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`lcsc`	Yes
`pads`	Yes
`pins`	Yes
`files`	Yes
`source`	Yes
`symbol`	Yes
`library`	Yes
`warnings`	Yes
`footprint`	Yes
`model_wrl`	Yes
`symbol_id`	Yes
`model_step`	Yes
`library_dir`	Yes
`footprint_id`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 12, 2026

TDQS

A4.3/5.0

Behavior4/5

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

Annotations already cover safety (readOnlyHint=false, idempotentHint=true, destructiveHint=false), so the bar is lower. The description adds important context beyond annotations: the data comes from EasyEDA user/JLCPCB drafts, is converted by easyeda2kicad, and should be treated as 'drafts, never as verified'. It does not mention auth or rate limits, but for a local file-generation tool this is a strong addition.

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?

The description is front-loaded with what the tool produces, then the usage workflow, then the quality caveat. It is somewhat long, especially the first sentence with nested parentheticals, but every sentence contributes useful routing or trust context.

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?

With an output schema present, the description need not explain return values. It covers the tool's purpose, source of data, workflow placement, and a critical quality warning. It does not restate workspace or registration constraints already covered by the schema, but those are available in structured fields.

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 83%, so the schema already documents most parameters. The description mentions the LCSC code and that files go 'into a library next to the project', but it adds no syntax or behavioral detail for the parts enum, lib_dir, lib_name, overwrite, or project_path beyond what the schema provides. Baseline 3 is appropriate.

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 states a specific verb and resource: fetching/converting symbol, footprint, and 3D model for one LCSC code. It clearly distinguishes the tool from siblings by naming parts_search for stock lookup and fp_info/doc_page for validation, so an agent can route correctly without opening schemas.

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?

It gives an explicit workflow: 'A part swap becomes: parts_search for the code and stock, lib_fetch for the files, then fp_info and the datasheet drawing (doc_page) for the pad-for-pad check.' This names the alternatives and the sequence for using this tool, leaving little inference needed.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.