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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered; the description adds real value by disclosing the response payload (result values with units, the formula, the worked Given → Formula → Substitute → Result when derivable, and a solved-page URL). With no output schema, that return-shape disclosure is genuinely load-bearing. It omits failure behavior for unknown calculator ids or unit mismatches.

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?

A single front-loaded sentence with no filler — the action and its inputs come first, return details after. It is dense, enumerating four return components in one clause, but every clause earns its place.

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?

Covers the two things an agent needs beyond the schema: where ids/keys come from and what comes back, which matters since there is no output schema. Annotations handle the safety profile. Only edge-case behavior (invalid id, unit mismatch, unknown key) is left unaddressed.

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%, so both parameters are already documented, including the defaults rule and the slug example. The description reinforces that input keys must come from list_calculators and must be in the listed units, adding a modest constraint but no syntax beyond what the schema states. 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 and resource ('Run one calculator by id') and immediately scopes it to a single calculator with numeric inputs, which cleanly separates it from the sibling listing tools (list_calculators, list_constants) and get_constant. The parenthetical pointing at list_calculators as the source of ids tells an agent exactly where this tool sits in the workflow.

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?

Gives clear context: obtain the id from list_calculators, supply keys in the listed units, and missing keys fall back to defaults. It stops short of exclusions — it never says when NOT to use it or when to call get_constant instead of passing a constant as a numeric input, so no alternative routing is given beyond the id-sourcing prerequisite.

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