muster release v5.19.0

describe_tool states that the tool it describes is only reachable through call_tool. Its response gained an invocation line — Call it through the call_tool meta-tool: call_tool with {"name": "<tool>", "arguments": {...}}, arguments per inputSchema. Tools inside muster are not callable by name directly — only the meta-tools are. — which the meta-tool’s own description names, next to what it returns, and call_tool’s own description now states the rule itself (“Aggregated tools are callable only this way, never by their own name”), so a model reads it when it decides how to execute rather than only after a lookup. An MCP client sees only the meta-tools, so a model that took a name out of describe_tool and issued it as a tool call of its own got an error with nothing in the detail it had just read to recover from. The field is additive: description, inputSchema, server, kind and annotations are unchanged, and the consumers that parse the response (the muster CLI, the REPL describe) ignore what they do not know. Scenario: list-tools-paged.