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

Annotations already declare readOnlyHint=true, so the safety profile is covered; the description adds the genuinely useful behavioral detail that only names are returned, which prevents an agent from expecting ids/values. The endpoint string (POST /v1/rex/SystemValues/getValueCategories) is slightly at odds with the read-only nature of the call, but the annotation resolves that and nothing in the prose contradicts it.

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?

Two sentences plus the endpoint: what it returns, what it's for, and what to do next, in that order. No filler and nothing an agent must read past to reach the actionable guidance.

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 no-param, read-only catalog lookup with no output schema, the description supplies enough: the shape of the return (names), their purpose, and the next call. It could say whether the list is fixed or user-configurable and whether results are ordered, but that is a minor omission.

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 the baseline is 4 and there is nothing for the description to compensate for. No misleading param hints are given.

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?

Specific verb+resource ("The names of Rex's value lists") with a parenthetical that defines what a value list is (allowed ids for note types, reminder types, lead sources, property categories), which an agent would otherwise not know. It also clarifies the return is names only, not the values themselves, and points at rex_get_value_list as the consumer.

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?

Explicitly states the follow-on action ("Use a name with rex_get_value_list"), giving a clear discover-then-fetch workflow. It stops short of stating when not to call it or how it relates to the sibling rex_get_value_list's own input shape, so it's clear context without full routing guidance.

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