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

Beyond the annotations (readOnly, idempotent), the description discloses that the tool always returns the full set of cost, price, profit, marginPct, and markupPct regardless of which inputs are supplied. This behavioral detail is not captured in the annotations and adds meaningful transparency about output completeness.

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 sentences, no fluff, with the core verb and resource front-loaded. Every phrase earns its place: the input rule, the alternative input mode, and the output list are all packed efficiently without redundancy.

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?

Given the tool's moderate complexity (4 params, no required fields, conditional input constraints), the description fully covers the key nuance of which parameter combinations are valid. The output schema and per-parameter descriptions cover the rest, so the description is complete for an agent to invoke the tool correctly.

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?

While the schema already documents each parameter individually, the description adds crucial combinatorial semantics: that only certain input pairs are valid and that supplying both cost and price is also acceptable. This goes beyond per-field descriptions and helps the agent understand the relationship between parameters.

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?

The description uses the specific verb 'Convert' with the resource 'margin and markup', immediately clarifying the tool's function. It clearly distinguishes itself from sibling financial calculators by naming its exact domain and the output fields it returns.

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 description provides explicit input combination rules ('Supply any one of cost/price plus one of marginPct/markupPct (or both cost and price)'), giving clear context on how to invoke the tool. It doesn't explicitly name alternatives or when not to use it, but the unique scope makes the usage context unambiguous.

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