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

Annotations already establish the read-only safety profile, and the description adds substantial non-obvious behavior: withdrawn listings fail with 'No listing', image_urls is always empty, and no description text is returned because it belongs to the advertiser at source_url. This is exactly the kind of context an agent cannot get from structured fields.

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?

The return contents are front-loaded in the first sentence, followed by useful edge-case notes. It is slightly repetitive, since 'advertiser's, at source_url' is stated twice in quick succession, but the overall structure is efficient and scannable.

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 an output schema present, the description needn't enumerate return values, and it still covers the key gotchas (inactive-listing failure, always-empty image_urls, absent description text). Nothing an agent needs to call this correctly is missing.

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 the schema already documents 'id' (from search_listings) and the 'wohnung'/'haus' fallback behavior of 'property'. The description adds no additional parameter semantics, so the baseline of 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 description states a specific verb and resource: it returns 'Details of one listing: facts, Somantic's valuation, and the link to the original.' This clearly distinguishes it from search_listings (plural) in spirit, though it never explicitly contrasts itself with the sibling tools by name.

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 implied rather than stated: the agent infers this is the follow-up call to fetch a single listing, and the id link to search_listings appears only in the schema. The note about inactive listings failing is a useful context cue, but there is no explicit when-to-use/when-not guidance or named alternative.

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