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Last modified June 21, 2026

Muster meta-tools reference

Muster exposes a small, fixed set of meta-tools to an AI agent instead of the hundreds of underlying tools behind the gateway. The agent discovers what it needs on demand and pays context cost only for the tools it uses. For the concept and the reasoning, see Meta-tools and tool discovery. This page is the field-level reference, verified against Muster v0.10.0.

The meta-tools

Muster exposes 11 meta-tools:

Meta-toolPurpose
list_toolsList all available tools from connected MCP servers
filter_toolsDiscover tools cheaply, with a bounded, summarized page
describe_toolGet the full description and input schema for one tool
call_toolExecute a tool by name with the given arguments
list_core_toolsList Muster’s built-in tools only
list_resourcesList all available MCP resources
describe_resourceGet details about one MCP resource
get_resourceRetrieve a resource’s contents
list_promptsList all available MCP prompts
describe_promptGet details about one MCP prompt
get_promptGet a prompt with the given arguments

The agent sees only these meta-tools in its MCP configuration. It shortlists candidates with filter_tools, inspects the chosen one with describe_tool, and runs it with call_tool.

Discovering tools with filter_tools

filter_tools is the discovery tier. It returns a bounded page of one-line summaries rather than every full description and schema, so the agent spends context only on plausible candidates.

Arguments

ArgumentTypeDefaultDescription
patternstringGlob match against tool names. Supports *. Case-insensitive unless case_sensitive is set
description_filterstringCase-insensitive substring match against tool descriptions
querystringNatural-language query. When set, matches are relevance-ranked with Okapi BM25 over each tool’s name and summary, returned best-first with a score, and non-matches are dropped
labelsobjectLabel facets as key=value pairs. A tool must carry every requested label to match. Labels come from a workflow’s metadata.labels
case_sensitivebooleanfalseWhether pattern matching is case-sensitive
include_schemabooleanfalseWhen true, each entry carries its full description and input schema instead of a one-line summary. This costs much more context
limitnumber5Maximum tools returned in this page. Raise it to page through more matches
offsetnumber0Number of matching tools to skip before this page

Response

The response is a bounded summary page:

{
  "filters": { "...": "the filter arguments applied" },
  "total": 12,
  "truncated": true,
  "tools": [
    {
      "name": "x_prometheus_query",
      "summary": "Run a PromQL query against a managed cluster.",
      "score": 4.21,
      "labels": { "category": "observability" }
    }
  ],
  "total_tools": 213,
  "filtered_count": 5
}
FieldDescription
totalNumber of tools matching the filters across the whole catalog
truncatedtrue when more matches exist beyond this page, the signal to page further or refine the query
toolsThe current page. Each entry has name, plus summary (or description when include_schema is set), score when ranked by a query, labels when present, and inputSchema when include_schema is true
total_toolsThe size of the full catalog. Retained for backward compatibility
filtered_countThe current page size, equal to len(tools). Deprecated: prefer total for the match count

describe_tool stays the authoritative source for a tool’s full description and input schema. Use filter_tools to shortlist, then describe_tool on the chosen tool before you call it.

Tool naming

Every tool reachable through call_tool falls into one of three families, distinguished by prefix:

  • x_<server>_<tool>: a tool from an external MCP server, prefixed with the server name to avoid conflicts, for example x_kubernetes_get_pods.
  • core_<area>_<tool>: one of Muster’s built-in tools.
  • workflow_<name>: a tool generated from a Workflow resource.

When an MCPServer declares a family, its tools are exposed under the family name (<prefix>_<family>_<tool>) with a required argument that selects which instance handles the call. See MCPServer.

Built-in tool catalog

Muster’s core_* tools manage the resources it owns. List them at runtime with list_core_tools, or muster list tool --filter 'core_*'. The catalog as of v0.10.0:

AreaTools
Authenticationcore_auth_login, core_auth_logout
Configurationcore_config_get
MCP serverscore_mcpserver_list, core_mcpserver_get, core_mcpserver_create, core_mcpserver_update, core_mcpserver_delete, core_mcpserver_validate
Servicescore_service_list, core_service_status, core_service_start, core_service_stop, core_service_restart
Workflowscore_workflow_list, core_workflow_get, core_workflow_create, core_workflow_update, core_workflow_delete, core_workflow_validate, core_workflow_available, core_workflow_run, core_workflow_execution_list, core_workflow_execution_get
Eventscore_events