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

Annotations already declare idempotent=true, destructiveHint=false, readOnlyHint=false; the description adds value beyond that with cost/performance traits ('free and instant — no rendering, no credits') and a real safety caveat about not applying an unchosen regenerated design just to tidy state.

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?

Front-loads the action and its cost profile, then layers the input sources and the two user-confirmation rules. Dense but every sentence carries an instruction; the account-selection rule is slightly generic but still actionable here.

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 no explanation. For a 3-parameter mutation the description covers cost, input provenance, a state-tidying trap, and multi-account disambiguation — everything needed to call it correctly.

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%, so the baseline is 3, but the description goes further by mapping templateImageUrl to three distinct sources and tying the pendingMediaUrl case to workspaceStatus 'pending_apply'. Some overlap with the schema's own templateImageUrl description limits it to a 4.

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?

States a specific verb and resource — making an existing design variation the active one on a Pin. 'Existing design variations' implicitly separates it from regenerate_pin_design and revert_pin_design, though neither sibling is named directly.

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?

Gives concrete entry paths (get_pin_design variations, a regeneration's variationUrl, a pendingMediaUrl) and names the decisive conditions: confirm with the user when a regenerated design hasn't been chosen, and ask which account when list_accounts returns multiple. Explicit when/when-not guidance with named prerequisite tools.

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