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

Beyond the readOnlyHint and idempotentHint annotations, the description honestly discloses current error states (`not_found`, `credentials_required`), the dependency on ETSY_KEYSTRING/ETSY_SHARED_SECRET, and the Etsy API quirk regarding `views`. It also notes the upstream deployment status, which is valuable behavioral context for an agent.

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 description is two sentences that pack in the core purpose, the unique `views` behavior, the operational status, and the two relevant error modes. Every phrase earns its place; no filler or duplication.

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 conveys that the response is 'full detail' and specifically flags the `views` field as populated only here. It also explains expected error modes and credential prerequisites. While it doesn't enumerate all return fields, 'full detail' plus the unique field mention sufficiently covers this simple get-by-id tool given its siblings provide context.

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?

The input schema already provides descriptions for both `language` and `listing_id` (100% coverage). The description adds minimal parameter-specific semantics: it reiterates the importance of `listing_id` via 'by id' and mentions credential requirements, but does not enrich the meaning of the `language` parameter beyond the schema. Baseline 3 is appropriate.

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 opens with 'Get one Etsy listing by id, full detail' – a specific verb (get), resource (Etsy listing by id), and scope (full detail). It explicitly distinguishes itself from sibling search and shop-listing tools by calling out the unique `views` field behavior, making the purpose unmistakable.

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 description provides clear context for when to use this endpoint: when a single listing's full detail is needed, especially if `views` is required, since search and shop-listings endpoints return `views: null`. It names the alternative categories (search and shop-listings) without being exhaustive, but the core usage trigager is stated.

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