Create a branch of an existing session, optionally at a specific message, to test changes or continue work without affecting the original session.
Fork an existing session, optionally at a specific message.
| Name | Required | Description | Default |
|---|---|---|---|
| id | Yes | ||
| directory | No | Project directory to target. Optional; defaults to the server default project. | |
| messageID | No |
Changes observed during successful MCP inspections.
v3.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It says nothing about whether messages are copied, what happens to the source session, permissions required, or whether the new session ID is returned – important gaps for a session-mutating 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?
A single front-loaded sentence with zero filler; the fork action leads and the optional message anchor follows. Efficient, though its brevity contributes to the other gaps.
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 fork operation with no annotations, no output schema, and one-third parameter coverage, the description omits too much – no result handling, no copied-state explanation, no defaults for the optional parameter.
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 coverage is only 33%, with just 'directory' documented. The description does usefully explain what messageID means (the fork point), partially compensating, but 'id' and the return semantics of directory remain unelaborated.
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?
States a specific verb and resource ('Fork an existing session') and clarifies the message-level granularity, which inherently separates it from opencode_session_create. It doesn't explicitly name a sibling, so it stops short of a 5.
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?
There is no when-to-use guidance, no mention of when to prefer this over opencode_session_create, and no prerequisites (e.g. session must exist). The word 'optionally' hints at a default behavior but doesn't explain it.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.