create_branch

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It states 'without touching the parent session', which reveals that the operation is non-destructive to the parent. The fork action implies creation of a new session, and the lifecycle mention of close_session/merge_branch hints at the branch's temporary nature. It does not cover all conceivable side effects (e.g., data isolation level), but the description is reasonably transparent for the tool's complexity.

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 two sentences, front-loaded with the core action, then usage context, then lifecycle guidance. Every phrase earns its place; no fluff or repetition. It is concise yet informative.

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 2-parameter tool with no output schema, the description covers the essential context: purpose, when to use, and post-branch actions. It does not explain return values or error behavior, but those may be inferred from the schema and the tool name. The lack of an output schema means the description need not describe return format. Overall, it is sufficiently complete for an agent to select and invoke the tool correctly.

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 100%: both session_id and version_id have descriptive schema text. The description does not add parameter-level detail beyond the schema. Per the rubric, baseline 3 is appropriate when the schema fully documents parameters, and the description provides no additional semantic value for them.

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 opens with 'Fork a new session from an existing one' – a specific verb and resource that clearly defines the tool's purpose. It further distinguishes from siblings by referencing close_session and merge_branch as lifecycle actions, indicating it is the branching tool in a session-management workflow.

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?

Explicitly states when to use: 'Use this to isolate an experiment, explore an alternative modeling approach, or try a risky edit without touching the parent session.' It also provides lifecycle guidance (close_session if it fails, merge_branch if it succeeds), which gives clear context. It does not explicitly name alternative tools to use instead, but the guidance is specific enough to differentiate its role.

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