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

Annotations already declare readOnly=false, idempotent=false, destructive=false, openWorld=false. The description adds genuinely useful behavioral context beyond that: confirm=false acts as a preview/dry-run, and retention_days has a 1-180 validation range. It does not mention required permissions or post-creation effects, keeping it below 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?

Front-loads the purpose immediately, then layers the parameter guidance. The event enumeration is long but every value earns its place by tying to a distinct retargeting intent. It is dense but not 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. For a non-idempotent mutation tool, the description covers preview behavior, input constraints, and the key parameter value space, leaving only permission requirements unstated. Adequately complete.

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%, so the description must compensate. It documents pixel_id's source, retention_days' valid range, and extensively enumerates and interprets event values (which lack an enum in the schema), plus confirm's preview semantics. Only account_id and name go unmentioned, but they are largely self-evident.

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 website retargeting audience from a pixel.' This clearly distinguishes it from siblings like create_meta_lookalike_audience, create_meta_engagement_audience, and create_website_audience. An agent can identify the tool's function without opening the 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?

Provides clear context for when to use specific event values (cart/checkout abandoners, buyers to exclude or seed lookalikes) and points to list_meta_pixels as the source for pixel_id. However, it names no alternative tool and gives no explicit when-not guidance versus the other audience-creation siblings.

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