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

With no annotations, the description carries the full behavioral burden. It implies a pure, side-effect-free calculation, but never states that it is read-only/deterministic or describes what the response contains. For a calculator the risk is low, but the disclosure is thin.

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?

Purpose is front-loaded in the first clause and the description is only two sentences. The three example questions are slightly redundant with the opening sentence, which is the only wasted space.

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 simple three-parameter calculator with no output schema and no annotations, the description covers the use cases and inputs adequately. The main gap is that return values (e.g., margin %, markup %, computed price) are only implied rather than stated.

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%, and the schema already explains cost, price, and targetMarginPercent, including the conditional 'optional if targetMarginPercent is given' relationship. The description only restates 'from cost and price' and a 40% margin example, adding no format, unit, or interaction detail beyond the schema, so 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?

The description names specific verbs (convert, work out) and precise resources (profit margin, markup, required price), so an agent immediately knows this is a margin/markup calculator. It does not explicitly contrast itself with the finance siblings (break_even, ebitda, etc.), but the domain is distinct enough that confusion is unlikely.

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 three quoted example questions ('what is my profit margin?', 'what is the difference between margin and markup?', 'what should I charge for a 40% margin?') give concrete context for when to invoke the tool. There are no stated exclusions or named alternatives, which keeps it short of a 5.

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