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+---
+rule: mcp-tool-invocation-must-be-documented
+title: MCP tool documentation must include the invocation model
+category: mcp
+severity: warning
+version: 1
+---
+
+# MCP tool documentation must include the invocation model
+
+## Rule
+
+An MCP agent's documentation must describe the actual invocation model — including
+whether a tool call is direct or wrapped via a generic action tool with a parameter value.
+
+## Why
+
+MCP servers may expose a small set of generic tools (e.g. `bc_actions_invoke`) that
+accept an action name as a parameter, rather than exposing each action as a named tool.
+
+When documentation lists action names (e.g. `List_Projects_PAG6102901`) without
+specifying that they are parameter values — not direct tool names — agents attempt to
+call them directly, fail with `InputValidationError`, and spend time diagnosing a
+documentation gap rather than a code error.
+
+## What to document
+
+For each MCP capability, the documentation must state:
+
+- The actual tool name to call (e.g. `bc_actions_invoke`)
+- How to discover available actions (e.g. `bc_actions_search`)
+- How to inspect an action's schema before invoking (e.g. `bc_actions_describe`)
+- The parameter that carries the action name (e.g. `ActionName`)
+
+## Example — correct
+
+> Tools are called via `bc_actions_invoke` with `ActionName` as the parameter.
+> Use `bc_actions_search` to discover available actions.
+> Use `bc_actions_describe` to inspect a specific action's schema before calling.
+
+## Example — incorrect
+
+> Call `List_Projects_PAG6102901` to list active projects.
+
+This implies a direct tool call. If `List_Projects_PAG6102901` is an `ActionName`
+value passed to `bc_actions_invoke`, this documentation will cause agents to fail.
+
+## Applies to
+
+Any CURABIS agent documentation that describes how to use an MCP tool.
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