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

Annotations already declare readOnly/openWorld/non-destructive, so the safety profile is covered. The description adds two useful facts beyond that: results are scoped to the calling account ('the account's') and the default payload is a limited field set. It says nothing about pagination behavior, default time window, or ordering, which matter for a 7-parameter list endpoint.

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 distinguishing qualifier, with zero filler. The trailing 'GET /clients/supplemental' is marginal value but harmless.

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 read-only list with fully documented params and no output schema needs little, and the description covers scope and default field set. However, it omits result shape, pagination/limit behavior, and what supplemental records actually contain, leaving an agent to guess at return structure.

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%, so every parameter is already documented with defaults, ranges, and the rf/['*'] convention. The description's 'basic set of fields' loosely echoes the fields parameter but adds no syntax or interaction detail. 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?

States a specific verb and resource and qualifies the resource as 'supplemental (non-MLS)', which materially separates it from idx_list_featured_listings, idx_list_off_market_listings, and idx_list_sold_pending_listings. It does not explicitly name those siblings, but the '(non-MLS)' qualifier does the core differentiating work.

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 guidance on when to pick this tool over the other listing listers in the sibling set, and no prerequisites or exclusions. The agent must infer selection purely from the word 'supplemental'.

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