body_replace_face

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

With no annotations, the description carries the behavioral burden well: it discloses the body-growth/shrink effect, invalid-target behavior with INVALID_PARAMS and no changes, and FUSION_API_ERROR with rollback. It does not cover permissions or idempotency, but mutation and failure semantics are substantially explained.

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 core operation, then organizes refs, errors, return keys, and an example into compact sections. Every line contributes actionable information without unnecessary prose.

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?

No output schema exists, so the description usefully names the return keys and error cases, and the example clarifies invocation. It could further clarify return-value meanings such as health, but is otherwise complete for this CAD mutation tool.

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 all three parameters are already documented in the schema, including tangent_chain's default. The description reinforces ref sources and target validity but adds little parameter-level meaning beyond the schema, matching the baseline for high schema coverage.

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: replace faces of a body with a target face, plane, or surface body, and describes the geometric effect (body grows or shrinks). This clearly distinguishes it from face-deletion or offset operations.

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?

Provides valid sources for face refs, planes, and surface bodies, and explicitly says a solid body is not a valid target. It stops short of naming when to choose sibling tools like body_delete_faces or feature_offset_faces, but the usage context is clear.

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