measure_list_reference_objects

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

With no annotations, the description carries the behavioral burden and does disclose non-obvious traits: the disc vs. card corner convention ('discs: bbox'), the clockwise-from-top-left ordering, and the downstream effects on depth, field of view, and footprint measurement. It is a read-only listing call with no parameters, so little risk remains undisclosed.

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?

Three sentences with no filler; the enumerated keys are front-loaded so an agent immediately learns what the tool returns. The middle sentence is dense with inline JSON and a parenthetical, which slightly slows parsing but every clause carries information.

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 zero-parameter listing tool with an output schema and full schema description coverage, the description covers everything an agent needs: what the list contains, where the physical object must be placed, and why the reference is required. Return-value details are correctly left to the output 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?

This tool takes zero parameters, so the baseline is 4. The description goes further by documenting the shape of the `reference` argument the returned keys feed into (type plus four pixel corners, or bbox for discs), which is genuinely useful context even though it technically belongs to a sibling tool's schema.

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 ('List everyday objects of known size') and enumerates the exact keys returned (credit_card, us_quarter, us_letter, a4, half_sheet_pan, dollar_bill). The purpose — supplying a metric scale reference for measurement tools — is unambiguous and clearly distinct from siblings like measure_object or measure_depth_info.

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?

Explicitly states when the returned reference matters ('Needed for relative depth; it also fixes a guessed field of view, and measures a flat object's footprint in a plain photo') and gives the physical precondition ('lay it flat on the same surface ... fully visible'). It does not name alternative sibling tools or when a reference is unnecessary, so it falls short of a full 5.

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