maestro

Overview Schema Source Related Servers Discussions Admin

launch_sessions

Launch multiple Claude Code sessions in parallel with one call, each blocking until ready; failures stay isolated while remaining sessions start, with a max parallel cap.

Instructions

Launch several sessions at once, in parallel. One call for a whole fleet.

Each entry takes the same fields as launch_session: agent_profile, session_name, working_directory, model, initial_message, use_worktree. Every launch still blocks until its Claude is ready, so a failure is reported against its own entry and the rest still start; max_parallel (1-8) caps how many start at the same time.

Ten sessions launched one by one cost ten calls and several minutes of waiting; this is one call and about as long as the slowest one.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "sessions": "<sessions>"
    },
    "name": "launch_sessions"
  }
}

Input Schema

Name	Required	Description	Default
`sessions`	Yes
`max_parallel`	No

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.3Oct 21, 2026

TDQS

A4.3/5.0

Behavior4/5

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

With no annotations at all, the description carries the full burden and does so well: it discloses that each launch blocks until its Claude is ready, that failures are isolated per entry while the rest still start, and that max_parallel (1-8) throttles concurrency. It omits permission/auth requirements and any rate-limit or side-effect profile, which keeps it from a 5.

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?

Front-loaded with the core purpose, then parameters, then a justification sentence. The third paragraph's cost comparison is decision-relevant rather than filler, though it is somewhat repetitive of the opening 'one call' framing.

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?

An output schema exists, so return values need no explanation. Given a batch tool with an undocumented nested array, the description supplies the field list, concurrency cap, and failure semantics an agent needs to call it correctly, though it could say more about what a partial-failure result looks like.

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

Parameters4/5

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

Schema description coverage is 0%, so the description must compensate, and it does: it enumerates the per-entry fields (agent_profile, session_name, working_directory, model, initial_message, use_worktree) that the opaque sessions array schema does not document, and gives the 1-8 range for max_parallel. It does not explain the type/format of individual fields or the max array length, but coverage is substantially better than the schema alone.

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 ('Launch several sessions at once, in parallel') and immediately frames the scope distinction from the sibling launch_session ('One call for a whole fleet'). An agent can tell this is the batch variant without opening the schema.

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?

Provides a clear rationale for choosing this tool over repeated launch_session calls ('Ten sessions launched one by one cost ten calls ... this is one call'). It lacks an explicit when-not-to-use (e.g. single session, or when per-session control matters), 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.