Rewind to a checkpoint

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

Annotations already flag destructiveHint and idempotentHint, so the description is not obligated to cover safety. It still adds real value beyond them: it says later checkpoints are dropped (a non-obvious side effect beyond the data rollback), that fault dice are restored so replay is deterministic, and that the response carries the new status.

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?

Three short sentences, each carrying a distinct fact (what rolls back, what is dropped, what is returned), with the destructive scope front-loaded. No filler.

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 one-parameter, no-output-schema tool with destructive annotations, this covers the effects and the response shape adequately. A brief word on failure when the checkpoint name is unknown would close the remaining gap.

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% and the single parameter is documented there as 'A checkpoint's name, as given to twin_checkpoint'. The description adds no syntax, format, or lookup guidance beyond that, so the schema is doing all the work.

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 concrete verb and resource ('Undo everything recorded after a checkpoint') and enumerates the state that is rolled back (records, twin time, fault dice). It is distinguishable from twin_reset and twin_checkpoint by its checkpoint-scoped nature, though it never names those siblings explicitly.

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?

Usage is only implied: an agent can infer you call this when you want to replay from a known point, but the description never contrasts it with twin_reset (full reset) or twin_load_scenario (scenario switch), which are the obvious alternatives an agent must choose between.

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