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

With readOnlyHint=true and openWorldHint=false already declared, the description still adds genuinely useful operational context: a 10-calculations-per-day-per-IP anonymous limit and the exact Authorization header format for a Premium key. It does not explain error behavior or what the result object looks like.

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 tight sentences with the core action front-loaded, followed by auth/limit details. Every sentence carries information; only the redundant restatement of 'returns the result' is marginal.

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 read-only, nested-input tool with no output schema, the description covers action, cost/rate limits, and auth. The only gap is the shape of the returned result, which 'returns the result' leaves unspecified, though a calculator's output is largely predictable.

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 (slug, inputs) are already documented in the schema, including the nested number map. The description adds no parameter-level detail, which is the correct baseline when the schema does the heavy lifting.

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 ('Runs a MonsiTools calculator') plus the immediate effect ('returns the result'). This is clearly distinguishable from describe_calculator and search_calculators, which are discovery tools, though the description never names those siblings explicitly.

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?

Usage is implied rather than stated: an agent can infer it should call search_calculators first to obtain a slug, but only because the schema says so, not the description. There is no explicit when-to-use/when-not guidance or routing to alternatives.

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