Add a mate connector

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

Annotations carry only a title, so the description bears most of the disclosure burden: it correctly frames the operation as creating a feature via inference and discloses that the return value is a feature id. It does not mention that this mutates the assembly feature list, whether the connector is persisted, or what happens if 'validate' fails beyond what the schema already spells out. Useful context, but an incomplete behavioral picture for a mutation.

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?

Two tight sentences with the core action front-loaded and the downstream dependency in the second clause; nothing extraneous. It could be marginally clearer by naming the return type explicitly ('returns the feature id'), but there is 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 7-param mutation with no output schema, the description does cover what the agent most needs: what gets created, how it's inferred, and that the output feeds onshape_assembly_mate. The one real gap is the absence of any note on error behavior or side effects, which 'validate' hints at only in the schema.

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 description coverage is 100%, so every parameter (doc/ws/elem/occurrence/name/validate/inference) is already documented with defaults and URL-segment hints. The description only echoes the inference examples already present in the schema, adding no syntax or value guidance beyond it — baseline 3 applies.

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?

The description states a specific verb and resource — 'Place an implicit mate connector on an instance by inference' — and immediately ties it to the sibling that consumes its output ('what onshape_assembly_mate then joins'). The parenthetical inference examples (CENTROID, TOP) make the mechanism concrete, so an agent can distinguish this from onshape_assembly_mate and onshape_assembly_add_feature.

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 sequencing hint ('Its feature id is what onshape_assembly_mate then joins') tells the agent this is a prerequisite step in the mating workflow, which is genuine when-to-use guidance. It stops short of explicit exclusions — e.g., it never says when to use an explicit mate connector feature instead of inference — so it earns a 4 rather than a 5.

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