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

Annotations already cover the safety profile fully (readOnly, idempotent, closed-world, non-destructive), so the bar is lower. The description adds genuine context the annotations cannot: data provenance (CODATA 2022, NIST values) and the fact that results are grouped. It does not describe the return envelope, which matters somewhat since no output schema is declared.

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 clauses, front-loaded with the resource and provenance before the filter detail. No filler, though the phrasing 'the constants UsePhysics keeps' is slightly informal relative to the otherwise technical register.

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-required-parameter read tool with rich annotations, the description covers provenance, grouping, and filtering, which is what an agent needs to select and call it. The main residual gap is the shape of the returned grouping, which cannot be inferred without an 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?

Schema coverage is 100% and the schema already documents the group parameter, including the example id. The description only restates that the filter is optional over a grouped result, adding no format or validation detail beyond the schema, so the baseline 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 the specific resource (CODATA 2022 physical constants) and the organizing shape (grouped, with an optional group filter), which is enough to separate it from get_constant and list_calculators. It never names those siblings explicitly, so the differentiation is inferred rather than stated.

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 phrase 'optional group id filter' implies the two usage modes (list everything vs. narrow to one group), but there is no explicit guidance on when to prefer this over get_constant for a single value, nor any prerequisite or exclusion. Usage is implied rather than prescribed.

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