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

readOnlyHint=true already covers safety, so the description's value-add is the enumeration of returned fields (property, tenants, lease dates, rent) — meaningful because there is no output schema. The endpoint note clarifies that a "read" is performed via POST, which prevents a wrong assumption about the HTTP verb. No mention of permissions or error cases, keeping it below 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?

Two short sentences, front-loaded with the resource and its payload. The trailing endpoint path is the only element of marginal use to an agent, slightly diluting otherwise tight phrasing.

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?

A single-parameter read tool with no output schema is adequately covered: input provenance and returned fields are both stated. Nothing critical is missing for correct invocation, though auth or not-found behavior would round it out.

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?

With one parameter at 100% schema coverage, the schema already defines id as a positive integer. The description adds provenance the schema cannot express: the id must originate from a search or autocomplete call, which guides correct value sourcing. That is genuine additive meaning above baseline 3.

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+resource: fetch one tenancy by id, and enumerates the payload it covers (property, tenants, lease dates, rent). This cleanly separates it from rex_search_tenancies, which returns many. It stops just short of naming the sibling outright, but the single-record scope is unambiguous.

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?

"The id comes from a search or autocomplete" tells the agent where to get the required input, implicitly routing to rex_search_tenancies / rex_autocomplete_* when no id is on hand. The prerequisite (must already have an id) is clear, though there is no explicit "do not use for listing" exclusion.

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