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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the tool is known safe. The description adds substantial behavior beyond that: response shape details (camelCase fields), size measurements (12.5 KB vs 1.6 KB trimmed), trim effects (which fields dropped/kept), and the shortcode 404 failure mode. This enriches the agent's understanding of runtime behavior.

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 detailed but every sentence earns its place: primary action, response shape, trim behavior, alternatives, and a concrete failure pattern. It is front-loaded with the core purpose and keeps the length proportionate to the complexity. No fluff or repetition.

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?

The tool is a fetch-by-URL with a known output schema. The description covers input validation (numeric URL), response size and shape, trim behavior, error handling (404 on shortcodes/deleted pins), and routes to sibling tools. Nothing an agent needs to call it 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 coverage is 100% (both url and trim are described in the schema). The description adds crucial semantics: url must be numeric-only (shortcodes fail), and trim=true specifically drops richMetadata and category while keeping a listed set of fields. This goes well beyond the schema's one-line descriptions.

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 the exact verb ('Fetches'), the resource ('one pin by URL'), and the URL format ('pinterest.com/pin/<id>'). It distinguishes from siblings by naming get_pinterest_search (keyword search) and get_pinterest_board (paging through board), so an agent can tell them apart.

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?

It explicitly states when to use this tool vs. alternatives: 'To find pins by keyword use get_pinterest_search; to page through the board a pin sits on use get_pinterest_board.' It also gives a clear precondition (numeric trailing id) and warns of 404s on deleted pins, providing practical routing guidance.

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