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

Annotations already establish read-only, idempotent, non-destructive, closed-world behavior, so the bar is lower. The description adds the required auth context ('OAuth scope newsletter:read'), which is genuinely beyond the structured fields. It says nothing about pagination behavior for a listing tool, so it falls short of full behavioral coverage.

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 short sentences, zero filler, with the resource scope front-loaded and the sibling routing placed last where it is most useful. Every sentence earns its place.

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, and the annotations plus the auth-scope note cover the safety profile. What remains missing is pagination behavior (limit/cursor) and any hint about project_id, which matters for a listing call an agent may need to page through.

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 description coverage is 0% across all three parameters, so the description carries the full burden and mentions none of them. The limit/cursor pagination contract and the role of project_id are left entirely to inference from bare titles and defaults.

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 ('Read custom field definitions') and narrows scope to 'signup forms and merge tags'. It also names the sibling it is not ('Use get_newsletter_schema for document, filter and field definitions'), so an agent can separate the two without opening either schema.

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?

Explicitly routes the agent to get_newsletter_schema when document/filter/field definitions are wanted, which is a real alternative-selection rule. It stops short of a full when/when-not set (no statement about prerequisites or when this tool is the wrong choice for other data).

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