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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds nothing beyond that: it does not say whether the tip is included in the per-person amount, how rounding is handled, or whether the computation is purely local.

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 words contain no filler, but this is under-specification rather than disciplined conciseness. There is no structure to speak of and nothing front-loaded beyond a bare label.

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?

With no output schema, the description should explain what comes back (per-person share, tip amount, totals) and whether tipPct defaults to 0 when omitted. For a simple three-parameter calculator the schema covers inputs, but the return behavior is left entirely undocumented.

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%; total, people and tipPct each carry examples and constraints in the schema. The description contributes no additional meaning, so the baseline of 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?

"Split bill calculator" largely restates the tool name (planning_split_bill) and title (Planning Split Bill). The word "calculator" adds a small hint that this computes an arithmetic result rather than splitting a file, which does help distinguish it from pdf_split/pptx_split, but no verb or scope is given.

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 guidance, no mention of alternatives (e.g. planning_cost_of_living or planning_monthly_budget for broader budgeting), and no prerequisites. An agent must infer the use case entirely from the name.

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