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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds genuinely useful behavior context about returned provenance (source page and check date per fact), but says nothing about lookup failure behavior, freshness windows, or result size.

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?

A single front-loaded sentence with zero filler that packs the resource plus the three most relevant return characteristics. Nothing could be removed without losing information.

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 description must carry the return-value burden, and it only gestures at it ('every fact') without describing structure, field names, or shape. For a one-parameter read tool whose annotations cover safety, this is adequate but leaves the agent guessing about the response payload.

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 coverage is 100% and the single parameter is documented as 'the listing URL or its slug (the last part of the URL).' The description introduces no additional syntax, format, or validation detail, so the schema does all the work — 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?

The description states a specific retrieval verb and resource ('One listing') and goes further to enumerate what comes back: every fact, the source page per fact, and the verification date. This clearly separates it from the multi-item siblings (compare_listings, search_listings), though the description never names those siblings explicitly.

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?

Usage is only implied: 'One listing' signals single-item lookup by URL/slug, which contrasts naturally with search_listings and compare_listings. There is no explicit when-to-use statement, no mention of when to prefer a sibling, and no prerequisite or error guidance.

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