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

With no annotations, the description carries the full burden. 'Look up' implies a read-only operation, but nothing is said about what 'detailed information' actually contains, whether historical data requires anything special, error behavior for an invalid or unknown ABN, or any auth/rate-limit constraints.

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 efficient sentence with the resource front-loaded and zero filler. It is arguably too terse rather than too long, but structurally clean.

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 simple two-parameter lookup with fully documented schema this is close to adequate, but with no annotations and no output schema, the description leaves the agent guessing about what 'detailed information' returns and what happens on lookup failure.

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% (both 'abn' and 'includeHistorical' are documented in-schema), so the baseline is 3. The description adds no meaning beyond the schema and says nothing about the includeHistorical flag or expected ABN formatting.

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 ('look up') and a specific resource ('Australian Business Number'), and the phrase 'specific ABN' implicitly signals this is a direct-identifier lookup rather than a name search. It does not name the sibling abn_search_by_name, so the differentiation is left to inference.

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 use when it already has an ABN, and the sibling name 'abn_search_by_name' hints at the alternative path. There is no explicit when-to-use/when-not statement or reference to the sibling tool.

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