compare_to_reference

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

With no annotations and no output schema, the description carries the burden and does it well: it discloses the alignment approach, the exact 0.4 cm difference threshold, the returned structure (stretches, implicated parts, zone of gun vs rail attachment) and the overlay image. It stops short of saying whether it is read-only or writes any artifacts to disk.

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?

One long but information-dense sentence with a front-loaded label and a parenthetical clarifying the overlay colors; nearly every clause conveys computation or output detail. It is slightly overloaded and the colloquial opener carries less signal than a plain verb-resource statement would.

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 two-parameter, no-annotation, no-output-schema tool, the description covers the mechanism, the threshold, and the return contents in enough detail to call it correctly. Remaining gaps are side effects and whether the reference must pre-exist, both minor.

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% and both parameters carry their own descriptions in the schema, including the default reference id and the omit-build fallback. The description adds the measurement context but no parameter-level detail beyond what the schema already provides, so 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?

Names a precise operation (draws the build's side outline at the reference photo's scale, measures both outlines column by column) with a concrete threshold (>0.4 cm) and output. No sibling tool does anything comparable, so an agent can distinguish it immediately from list_references or build_gun.

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 framing 'the real-gun check' implies a verification-after-build use case, and the schema notes that omitting build falls back to the reference's own configuration, but the description never states when to reach for this versus list_references or build_gun, nor any prerequisites.

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