Fork a market session

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

Annotations already declare the safety profile (readOnly=false, destructive=false, idempotent=false), and the description adds traits they cannot express: the original is unchanged, the fork counts against the 8-session cap, and it 'runs no market' (no simulation cost). It also asserts determinism — identical steps yield identical prices in both sessions — which is exactly the kind of behavioral guarantee an agent needs when deciding to branch.

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?

Front-loaded with the core action and outcome, then the use case, then the constraints. Four sentences, each carrying information, though the opening sentence is dense enough to be read twice.

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?

An output schema exists, so return values need no explanation. The description covers state inheritance, side-effect profile, quota impact, and determinism — everything an agent needs to call this correctly and predict the result.

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?

Only one parameter, and schema coverage is 100% with the schema itself documenting the format ('exactly as open_session or session_fork returned it'). The description adds no further syntax or constraint detail, so baseline 3 is appropriate.

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 ('Copy an open session ... into a new session with its own id') and pins the copied state ('at its present state'), which cleanly separates it from open_session and session_rewind in the sibling list.

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?

Gives a clear motivating scenario — 'try two different actions from the same market and compare them' — which tells the agent when branching is the right move. It stops short of naming the alternatives (session_rewind, open_session) or stating exclusions, so it is strong context rather than full routing.

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