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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered; the description adds real value by disclosing that the payload is a static reference corpus and by naming a non-obvious rule (FIFO or specific identification, not weighted average). It stops short of saying whether the data is versioned/snapshot per year or what is returned when a tax year has no published rules.

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?

A single front-loaded sentence with a colon-introduced content list; nothing is padded or redundant. It is dense and long but every clause names a distinct returned item, so the length is earned rather than wasteful.

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 and a single trivial parameter, the description carries the burden of telling the agent what comes back, and it does so thoroughly by enumerating the rule categories. The only material gap is behavior at the edges — unsupported or future tax years and whether the response reflects a dated snapshot.

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% — the tax_year property already explains that it is the year the tax year ends and defaults to the current tax year. The description restates the same idea ('for a tax year') without adding format, valid range, or fallback behavior, 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 opens with a specific verb and resource ('Returns the South African crypto tax rules for a tax year') and then enumerates the exact contents returned (income tax table, CGT exclusion, inclusion rates, cost methods, treatment of swaps/gifts, CARF reporting). This clearly distinguishes it from siblings that compute figures (crypto_tax_estimate, crypto_gains_fifo) — this one is a reference lookup, not a calculation.

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?

Usage is only implied: an agent can infer this is the tool to consult for rules and rates rather than to compute a liability. There is no explicit 'use this when…' statement, no named alternative (e.g. 'for an actual liability, use crypto_tax_estimate'), and no note on what to do for years outside the supported range.

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