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

Annotations already cover readOnly, idempotent and non-destructive behavior, yet the description adds genuinely new operational facts: the call is FREE, failed calls are never charged, and project_token proves identity only — not the authenticity or freshness of the supplied state. The warning to keep full text client-side is also useful. It stops short of describing output structure or limits, so a 4.

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-loads the most important qualifier ('FREE') and then the purpose, with the authenticity caveat following. The bilingual restatement roughly doubles the length, which is defensible for a zh/en-targeted tool but does introduce redundancy. Every sentence otherwise carries weight.

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-format explanation is rightly omitted, and annotations cover the safety profile. The description supplies the non-obvious trust and billing context an agent needs. It is slightly thin on the tuning parameters (recent_chars, direction), which is the only material 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 only 20% across 5 parameters. The description adds real meaning for project_token (identity-only, not content validation) and implicitly covers lang (zh/en) and the state payload. However, recent_chars (window size), direction, and the idempotency behavior of request_id are left to the schema, so it does not fully compensate for the coverage gap.

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: 'Render a StoryState into a zh/en handoff document (recent-canon window + bible) for a successor writer/AI.' The purpose and output artifact are unambiguous. It does not explicitly name or contrast with siblings such as prepare_story_window or absorb_story_window, so it earns a 4 rather than a 5.

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?

The intended consumer (a successor writer/AI) implies the usage context, but there is no explicit when-to-use versus alternatives like prepare_story_window, nor any stated prerequisites or when-not-to-use conditions. Guidance is inferable but not spelled out.

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