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mpfb_list_rigs

Read-onlyIdempotent

List every standard, Rigify, and custom rig available for a MakeHuman basemesh in Blender without adding anything to the scene. Use the identifier to add a rig.

Instructions

List every rig this Blender could add to a MakeHuman basemesh: MPFB's bundled standard and Rigify rigs, plus custom rigs found in the user's data directories. Adds nothing to the scene.

Pass a rig's identifier, not its name, to mpfb_add_rig. The two are not the same string: a standard rig is "default_no_toes", a Rigify one "rigify.human", a custom one "custom.my_rig". The prefix also picks between MPFB's two non-interchangeable adding functions - add_function says which - and crossing them does not read as the mistake it is: a built-in name handed to the custom function comes back missing under a mangled one.

refresh=true rescans the user data directories for custom rigs first. MPFB caches that list for the lifetime of the Blender session, so a rig installed after Blender started will not appear otherwise.

result carries:

rigs: one entry per rig, with name, identifier, family ("standard"/"rigify"/"custom"), path (absolute, or null), label/description (MPFB's own UI text, null for custom rigs), add_function, available and unavailable_reason.
Per entry, what adding it would do about weights: has_weights, weights_path and weights_from. MPFB resolves weights through a fallback table, not by filename, so weights_from differs from name for default_no_toes (which borrows default's) and rigify.human (which borrows rigify.human_toes's). That is normal. has_weights: false is not: adding that rig produces a character with no vertex weights.
count, families, message, and rigify_available - whether Rigify is enabled here. Rigify rigs are listed either way, carrying available: false when it is not, since adding one then raises rather than degrading.
rig_dirs: every directory looked in, each flagged with whether it exists. MPFB scans its own data dir and the user data roots - not the MakeHuman user data directory.
unrecognized_custom_rig_files: .json files in a scanned user rigs directory that MPFB refused as rig definitions - a name outside [A-Za-z0-9_], or no identifying_bones key. MPFB drops these silently, which otherwise makes "I put the file there and it does not show up" undiagnosable.

Do not expect this list to match mpfb_get_object_info's rig_identified_as. That value comes from MPFB identifying an armature by its bone names and can be rigify_generated.* or unknown, neither of which names something addable. A character whose rig is not in this list is ordinary, not an error.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "mpfb_list_rigs"
  }
}

Input Schema

Name	Required	Description	Default
`refresh`	No

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Oct 3, 2026

TDQS

A4.5/5.0

Behavior5/5

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

Annotations already cover read-only/idempotent/no-op safety, and the description adds substantial context beyond them: session-lifetime caching, the weight fallback table (weights_from differing from name), that Rigify rigs are listed but raise on add when unavailable, and that unrecognized files are dropped silently. None of this contradicts the annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness3/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The essential identifier/add_function warning is bolded and front-loaded, but the lengthy enumerated 'result carries' section largely restates return fields that the output schema already documents. Some detail earns its place; a meaningful portion is verbose duplication.

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?

Given a single optional parameter and an existing output schema, the description is thorough — covering identifiers, refresh, availability, weights, and the deliberate mismatch with mpfb_get_object_info. The only shortfall is that the return-field documentation partly duplicates the output schema rather than adding new information.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters5/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 0% for the single `refresh` parameter, so the description must compensate — and it does: it specifies that refresh rescans user data directories first, and explains the caching consequence that otherwise leaves a newly installed rig invisible.

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 — listing every rig addable to a MakeHuman basemesh — and scopes it into named categories (bundled standard/Rigify, custom). It also implicitly differentiates from siblings like mpfb_add_rig and mpfb_get_object_info by explaining what each returns.

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 clear context for use and names the consuming sibling, warning to pass an `identifier` rather than a `name` to `mpfb_add_rig`, and explains when to set `refresh=true` (a rig installed after Blender started). It lacks an explicit when-not-to-use statement, so it stops short of a 5.

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