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

With no annotations and no output schema, the description carries the full burden and does disclose a genuinely non-obvious trait: the result includes a calculator_url that must be rendered as a clickable markdown link. It also implies the shape of the return (tip, total, per-person split), though it says nothing about rounding, negative/zero inputs, or currency conversion.

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 short sentences, front-loaded with what is computed and followed by the critical presentation instruction. No filler, though the opening is a noun fragment rather than a fully formed statement.

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 three-parameter calculator with no output schema and no annotations, the description covers the essentials: what is computed, the fields returned, and the required display behavior for the returned URL. Edge-case behavior (rounding, zero people) is the only meaningful gap.

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 documents all three parameters including defaults (people=1, tip_pct=20, bill in USD). The description adds nothing about parameter semantics beyond echoing the outputs, so the 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 the concrete outputs (tip amount, bill total, per-person split), and the tool name supplies the verb 'calculate'. It is specific enough that an agent knows exactly what it gets back, and no sibling tool covers tip splitting, so differentiation is implicit.

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?

There is no when-to-use or when-not-to-use guidance; the only directive concerns how to present the result, not when to invoke the tool. Usage is fairly self-evident from the name, which keeps this from being a 1, but nothing is stated.

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