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

readOnlyHint=true already establishes this is a safe read, so the description's job is to add context. It does add value by enumerating the data the record surfaces (vacancy, availability, unit type, market rent, location), which is meaningful for a tool with no output schema. It stops short of noting what happens for a missing/unknown id or how the vacancy/availability fields relate.

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?

It is short with no wasted prose, but it is a noun-phrase fragment rather than a front-loaded statement of action and scope, and the trailing endpoint string mostly restates what the tool is. Terse without being organized for scanning.

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, the field enumeration partially covers what the agent gets back, and readOnlyHint covers safety. However, for a record-fetch tool it remains thin: no behavior on invalid ids, no sense of payload size or relationships to get_property/get_tenancy.

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?

Coverage is 100% on the single parameter, and the schema already explains that the id comes from 'the corresponding list tool.' The description contributes nothing beyond that, 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 fragment list plus 'GET /v2/units/{id}' implies a single-unit retrieval, but the description never states the verb explicitly — an agent must infer it from the HTTP path. It does not distinguish this from the sibling arthur_list_units, which is the most likely confusion point.

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?

There is no when-to-use guidance whatsoever: nothing says to call this after arthur_list_units to fetch full details, and no alternative (e.g., arthur_list_units for a collection) is named. The agent is left to infer selection rules from the tool name alone.

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