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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered by structured data. The description adds only that the computation is sensor-width driven and derives two values. No rate limits, unit caveats, or edge-case behavior are disclosed, but with this annotation coverage a 3 is appropriate.

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, front-loaded with the core purpose. The second sentence is a useful signpost rather than filler, though it belongs more to usage guidance than to the purpose statement. Minimal waste.

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?

With only one fully-documented parameter and an output schema that covers return values, the description supplies what the agent needs to invoke the tool correctly. The remaining gap is the absence of usage context relative to sibling photography calculators.

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 the single parameter (sensor_width_mm) is fully documented in the schema, including the full-frame = 36mm reference. The description's 'based on sensor width' merely restates the schema, so the 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?

States a specific verb ('Calculate') and resource ('camera crop factor and equivalent focal length') with the input basis ('based on sensor width'). It is unambiguous what the tool does. It does not, however, contrast itself with the several photography siblings (calculate_depth_of_field, calculate_exposure_triangle, calculate_hyperfocal_distance), so it stops short of a 5.

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 only guidance is 'See list_bundles for related photographie calculators,' which is a navigation pointer, not a statement of when to use this tool versus alternatives. There is no mention of prerequisites, units assumptions, or exclusions. An agent gets no decision rule from the description.

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