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

Goes beyond the read-only/idempotent annotations by disclosing the inputs' merge contract (b holds only changed fields), naming the returned artifacts (per-check and per-year breakdowns, difference, PDF and CSV), and bounding scope. It does not mention error behavior or limits on the comparison, but the trait coverage is otherwise strong.

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?

Front-loaded with the use case, then the input rule, then outputs, then exclusions — a sensible order with no filler. The opening sentence is long because it packs in several example phrasings, which slightly blunts scannability.

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 two-object, deeply nested tool with an output schema, the description supplies everything needed to invoke it correctly: what to pass, how b relates to a, what comes back, and what the tool refuses to do. Return-value detail can safely be left to the output schema.

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%, so the baseline is 3. The description still adds real value by stating the split of labor between a and b ('give scenario a in full and scenario b with only the fields that change, everything else is copied from a'), which tells the agent how to construct the payload rather than just what each field means.

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 and resource ('compare take-home pay for two US paycheck scenarios in 2026 side by side') and immediately grounds it in recognizable user phrasings like state-to-state job offers and 401k changes. It is clearly distinguishable from calculate_paycheck by the two-scenario framing.

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?

Gives concrete triggering utterances ('should I take the job in Texas or California after taxes', raise, pay frequency change) and explicitly excludes out-of-scope uses: 'Does not compare cost of living, benefits, or run payroll.' Little 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.