devin_run_phase

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

No annotations are provided, so the description carries the behavioral burden. It does document the return format (success, session_id, url, error keys), which is helpful. However, it doesn't disclose side effects, auth requirements, rate limits, or what happens on partial failure. The return format disclosure is useful but incomplete for a session-spawning external tool.

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 description is well-organized with Args/Returns sections, making it scannable. Every sentence adds information. It's somewhat longer than the minimum, but the return-key documentation and parameter examples justify the length. Formatting is clean and front-loaded with the core purpose.

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?

The tool has an output schema, which offloads some completeness burden. With only 2 parameters (one optional) and a clear purpose, the description is reasonably complete. However, given it spawns external sessions, missing context about session lifecycle, expected duration, or relationship to devin_await_completion could confuse an agent about the asynchronous nature of the created session.

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 schema itself provides minimal help. The description compensates partially by explaining the prompt parameter with a concrete example and clarifying that playbook_id is optional if the env var is set. This adds real meaning beyond the schema, but there's no documentation of the playbook_id parameter's format or how to find valid IDs.

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 description clearly states the tool creates a new Devin session with a playbook and prompt. It uses a specific verb+resource construction and the context makes the purpose distinct from siblings (get_status, await_completion, send_message). However, it doesn't explicitly differentiate itself from sibling create-like tools, though none of the siblings appear to create sessions.

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 implies usage context (starting a new session), and the example prompt provides a meaningful usage template. However, it doesn't explicitly state when to use this tool versus alternatives, nor mention exclusions or prerequisites (like needing DEVIN_PLAYBOOK_ID or an existing plan document).

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