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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lowered; the description still adds real context: the output is a single iframe line, free, no sign-up, no cookies or tracking, and the widget is responsive and follows light/dark mode. It does not cover rate limits or attribution requirements, so it stops short of a 5.

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 and constraints are front-loaded, and the enum-to-name list earns its space by disambiguating identifiers. The enumeration is long but functional; nothing is wasted, though it is dense.

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?

An output schema exists so return shape needn't be described, and the description still states the return is HTML code. For a two-parameter read-only tool with clear scope and exclusions, an agent has everything needed to select and invoke it.

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%, so the baseline is 3, but the description maps every enum value to a human-readable calculator name ('rule_of_72 (Rule of 72 calculator)') far beyond the raw enum keys. The currency parameter is left entirely to the schema, which handles it adequately.

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+resource ('The HTML to put one of SmartFin's free calculators on a website') and explicitly carves itself out from the sibling calculate_* tools. An agent can distinguish this from the eight calculation tools without opening a schema.

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?

Explicit when-to-use ('user wants a calculator on their own site or asks how to add one') and when-not ('Do not use to calculate anything (use the other smartfin_ tools)'), naming the alternative tool family. Nothing is left to inference.

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