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

Beyond the annotations (readOnly, idempotent, closed-world), the description discloses two real behavioral traits: deadlines are pre-shifted to the previous business day per SARS rules, and each call costs $0.005 USDC via x402 on Base mainnet. It omits the response shape (e.g., whether entries carry labels/types), which keeps it from 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?

Coverage is front-loaded in one sentence listing the deadline types, followed by a short audience note and a pricing note; every clause carries information. No filler or repetition of the schema.

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 read-only, two-optional-parameter query with no output schema, the definition covers scope, date handling, business-day shifting and cost. The only meaningful gap is that it never indicates what a returned deadline entry looks like (date plus obligation label), which would help an agent use the results.

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 documents defaults, the YYYY-MM-DD format and the 400-day cap for 'from'/'to'. The description only restates 'between two dates' and adds no date semantics beyond the schema, 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?

States a specific resource and scope: SARS tax deadlines returned between two dates, and enumerates the covered obligation types (EMP201, VAT201, IRP6, EMP501, filing season). This clearly separates it from siblings like za_public_holidays or za_add_business_days without needing the 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?

Gives concrete usage context ('payroll, bookkeeping, accounting and tax compliance reminders in South Africa'), making the applicable scenario obvious. It does not name alternatives or exclusions (e.g., when to prefer za_public_holidays or za_add_business_days), so it stops short of the top score.

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