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

Annotations already declare the mutation profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false), so the lower bar applies. The description still adds non-obvious context beyond them: section creation consumes no Pin credits, and collaborator-owned board structure is immutable. It does not cover behavior on duplicate section names or failure modes, which would be needed for a 5.

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?

Three sentences, each carrying distinct and necessary information: purpose plus return value, cost, then the account-selection precondition. No filler and no restatement of the name or schema fields.

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 elaboration, and the description still names the section ID. With annotations covering the mutation profile, the description supplies the remaining decision-critical context: valid boardId source, cost, and account-selection behavior.

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. The description goes beyond it by constraining which boardIds are valid — those from list_boards, excluding collaborator entries — a selection rule the schema does not state. It adds nothing about the name parameter's 180-character limit or accountId resolution, but that is already in the schema.

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 ("creates a named section on a board") with the identifying key (boardId) and the return value (section ID). It is clearly distinct from create_board, update_board_section, and delete_board_section in the sibling list.

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?

Opens with an explicit trigger ("Use this when the user wants to add a section to a Pinterest board") and adds a real exclusion: boards that appear as collaborator entries in list_boards cannot be used. It also gives a concrete disambiguation rule for accountId when list_accounts returns multiple accounts, telling the agent to ask rather than guess.

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