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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds useful context beyond that by stating the data is 'public' and enumerating what comes back (bio, website, avatar, counts), which sets expectations for the response shape.

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 tightly written sentences: the core purpose and returned fields come first, and the sibling routing follows. Nothing is redundant or padded.

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?

An output schema exists, so return values need not be explained in prose; the description still summarizes them briefly. For a single-parameter read tool with full schema coverage and read-only annotations, nothing needed 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?

With 100% schema coverage and a single parameter already documented in the schema, the description's 'by `username`' adds no format or validation detail. Baseline 3 is appropriate when the schema does the heavy lifting.

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 (Fetch), resource (a Pinterest user's public profile data), the input key (by `username`), and enumerates returned fields. It also explicitly distinguishes itself from pinterest_user_boards and pinterest_user_pins, so an agent can tell it apart from siblings at a glance.

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 routes the agent to the correct alternatives (pinterest_user_boards / pinterest_user_pins) for user content, which clarifies the boundary of this tool. However, it never states explicitly when this tool is the right pick (e.g., 'use when you only need profile metadata') beyond the implicit contrast.

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