add_parts

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

With no annotations, the description carries the full burden and does disclose the most important behavioral trait: partial-failure semantics (colliding or invalid parts are skipped and reported, the rest still place). That is genuinely non-obvious and valuable. It stops short of stating idempotency, whether a failed batch is retryable, or permission requirements, so it is strong but not exhaustive.

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 short sentences, zero filler, with the core action front-loaded and the failure/return behavior following. Every 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?

An output schema exists, so return-format detail is largely covered (the description still notes new part ids). The main gap is usage context relative to siblings and any prerequisite/safety expectations for a mutation tool with no annotations.

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 top-level 'parts' parameter has no schema description, but the nested PartSpec fields (part, color, y, rot) are documented in the schema. The description adds only the cardinality hint 'one or more', which is marginal beyond what the schema provides, so a baseline 3 is appropriate.

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+resource ('Place one or more parts') with batch scope made explicit. It is immediately distinguishable from siblings like list_parts, remove_parts, and check_model without opening any schema.

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 description says nothing about when to reach for this tool versus alternatives. There is no mention of check_model for pre-validation, undo for reversal, or new_model/open_model as prerequisites, leaving the agent to infer placement context entirely.

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