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

The annotations declare a non-read-only, non-idempotent, non-destructive mutation, and the description adds real behavior beyond that: returning the scene to narrate plus following choices, returning the ending, and the rewind semantics of go_back. It stops short of stating what happens on an invalid or unmatched choice, or whether rewind discards prior path history.

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 sentences, front-loaded with the primary advance-the-story behavior, then the resume and rewind variants. Nothing is repeated and nothing is padding.

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?

With no output schema present, the description carries return-value disclosure and does it well by naming the three possible outcomes. The remaining gap is failure behavior and any constraints on whether go_back is allowed before an ending, but for a 4-parameter tool this is close to complete.

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%, so parameter meanings are already documented; the description nevertheless adds mode-level semantics the schema does not — absence of choice means 'resume' and go_back means 'return to last choice and choose again'. That is genuine added value over the structured fields.

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 — it advances a Plot Speaks choose-your-path story by the player's choice — and explicitly names what comes back (next scene and choices, or the ending). It is clearly separable from siblings such as pick_for_me or start_story because it is driven by a player-supplied choice within an existing play.

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?

It spells out three distinct call modes: pass a choice to advance, omit choice to resume and get the path so far, and set go_back to rewind to the last choice after an ending. That is concrete when-to-use guidance, though it never names a sibling alternative (e.g. pick_for_me) as the option when the player has no answer of their own.

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