spawn

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

Annotations already establish that the tool is non-readonly, non-idempotent, and non-destructive. The description adds meaningful contract context—it is the public MCP surface, parallel by nature, and deliberately excludes retry lineage/config fields—but it does not disclose other behavioral traits such as whether the call blocks on completion or what side effects spawning creates.

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

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

The core purpose is front-loaded in a single clear sentence, followed by a brief, relevant note about the public/private contract split. The second paragraph is somewhat esoteric but earns its place by explaining why certain fields are absent; overall it is compact with no wasted words.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a tool with 12 parameters and 0% schema coverage, the description is materially incomplete: it does not define any input semantics and gives no guidance on how the spawned child session behaves or relates to the many spawn/thread siblings. The output schema covers return values, but the input side is largely a black box.

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

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

Schema description coverage is 0%, so the description bears the full burden of explaining 12 parameters, yet it explains none of them. Parameters like slim, write_origin, permission_mode, capture_output, and extra_allowed_tools are opaque, and the only hint—'config fields do not leak'—concerns fields intentionally absent rather than the ones present.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The opening sentence 'Launch a new child session in parallel' gives a specific verb, resource, and distinguishing qualifier. It makes the core action unambiguous, though it does not explicitly differentiate from session/thread siblings like task_thread or idle_thread.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides one useful exclusion: watchdog continuation retries should use the private `_spawn_impl`, implying this public tool is for normal interactive launches. However, it gives no guidance on when to choose spawn over related siblings such as spawn_status, spawn_budget_set, or the thread-based session tools.

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