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

Annotations already declare readOnlyHint, idempotentHint and non-destructive, which is the whole safety profile for a stateless calculator. The description adds no further behavioural context (no note that it is a pure formula, no unit assumptions), so it neither helps nor contradicts the structured data.

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 short sentences, purpose front-loaded, no filler. It does restate inputs and returns that the schema and output schema already provide, so it is not perfectly economical.

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 deterministic calculator with an output schema, the description covers what is needed to call it correctly. The stray reference to an eyepiece field-of-view input is the only completeness blemish.

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% with only two numeric parameters, so the baseline is 3. The description adds no unit or range detail, and actually lists a third input ('eyepiece field of view') that does not exist in the schema, which is mildly misleading rather than helpful.

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 ('Compute telescope magnification, exit pupil, and field of view') and names the domain ('astronomy hobbyists'). No sibling calculator covers telescope optics, so the agent can select this one unambiguously.

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?

Offers only an audience cue ('Use for astronomy hobbyists') plus a pointer to list_bundles for related 'astronomie-nature' calculators. There is no when-not guidance, no prerequisites, and no contrast with neighbouring optical/photography calculators such as calculate_crop_factor or calculate_depth_of_field.

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