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

Annotations already declare readOnlyHint=false, destructiveHint=false and openWorldHint=true, so the safety profile is covered structurally. The description adds the platform-side audience type mapping, which is useful for interpreting errors, but says nothing about whether creation is reversible, what happens on duplicate names, or provider auth requirements — meaningful gaps for an open-world write.

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?

A single front-loaded sentence with no filler; the created resource and its origin both land immediately.

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?

With full schema coverage, no output schema and explicit annotations, the definition is nearly self-sufficient. The only missing piece is outcome information (what is returned or what to do after creation), which is minor for a create operation at this schema richness.

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 100% and every parameter, including the STATIC/DYNAMIC enum semantics and the no-'/' name constraint, is already documented in the schema. The description's mention of STATIC/DYNAMIC simply restates the variant enum, adding no new parameter-level meaning.

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 gives a specific verb and resource ('Create a Marketing-Automation-contacts custom audience') and even names the underlying platform types (MA_CONTACTS_STATIC/MA_CONTACTS_DYNAMIC), which lets an agent distinguish it from siblings such as create_salesforce_contacts_audience or create_audience_from_segment. It stops short of explicitly naming those alternatives, so it is clear but not fully differentiated.

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?

The phrase 'from a provider library list' implies the prerequisite (a library list id sourced elsewhere), but the description never states when to choose this tool over the other audience-creation tools or any when-not conditions. Usage is inferable rather than stated.

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