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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds genuine domain context beyond that: what the payload contains (IDs, names, synonyms, source links) and the important interpretation caveat that 'Therapy services' is a broad category, not proof a provider offers that therapy. It stops short of describing pagination or enumeration size, which would push it to 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?

Four short sentences, front-loaded with the triggering condition, then return contents, then a caveat, then the exclusion. Every sentence carries distinct information and none restates the title or annotations.

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?

An output schema exists, so return fields need only be named, which they are. With annotations covering safety and no parameters to explain, the description closes the remaining gap an agent would hit: what the categories mean and where they must not be applied.

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?

The tool takes zero parameters, so there is nothing to disambiguate and the description correctly spends no words on inputs. Baseline of 4 applies; a 5 is unnecessary since no parameter guidance is required.

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 (list NDIS directory service categories) plus exactly what is returned: category IDs, names, synonyms and source links. The opening clause ties it to a concrete task ('mapping a requested NDIS support ... before searching'), which separates it from get_ndis_provider and search_ndis_providers without naming them.

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 an explicit use case with sequencing ('before searching') and an explicit exclusion ('Do not use for NDIS billing item codes or funding advice'). The agent knows both when this tool is the right entry point and when it is the wrong one.

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