replay_step

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

With no annotations, the description carries the full burden and does well: it flags STATE_MUTATING, specifies the exact mutation magnitude (one bar), and states the precondition that Replay mode must be active. It does not cover edge behavior at the end of the replay range, which would be needed for a 5.

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 tight, labeled sentences (purpose, WHEN TO USE, SIDE EFFECTS, LIMITATIONS) with zero filler. The core action is front-loaded and each clause earns its place.

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 zero-parameter mutating tool with no output schema, the description covers action, precondition, and mutation semantics. The only gap is what happens when the replay reaches its end or is already past the limit, which an agent stepping repeatedly would want to know.

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?

The tool takes no parameters, so there is nothing for the description to disambiguate. Baseline 4 applies; the description correctly adds no spurious parameter detail.

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 precise verb+resource+scope: 'Advance replay forward by exactly one candle bar.' This clearly distinguishes it from siblings such as replay_autoplay (continuous) and replay_start (initialization).

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?

Explicit 'WHEN TO USE' clause names the condition (manual forward simulation, step-by-step). It implies the manual-vs-autoplay distinction but doesn't name replay_autoplay as the alternative for continuous playback, which would have made it a 5.

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