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

Goes well beyond the annotations by disclosing the 422 failure condition, the event_id uniqueness/dedup requirement, the SHA-256 pre-hashing of email and external_id, and the test_code routing behavior. The dedup note sits in mild tension with idempotentHint=false, but it applies only when a stable event_id is supplied, so it is not a genuine contradiction.

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 paragraph where each clause carries new information (event set, identifying key, error condition, hashing, test routing). Dense but no filler, though the packed style makes it slightly harder to scan than a bulleted form.

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?

For a 13-parameter, no-output-schema tool, the description covers the essential mechanics an agent must know: identity resolution, the ctwa_clid prerequisite, dedup semantics, hashing, and test routing. Remaining gaps (currency/value expectations, content_ids usage) are largely covered by schema descriptions.

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?

Adds meaning past the schema: chat_id and phone are framed as interchangeable identifiers, event_id as a dedup key, email/external_id as pre-hash inputs, and test_code as a routing switch. value, currency, content_ids, and dataset_id are left to the schema, but coverage there is already ~77%.

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 (Report) and resource (conversion event), enumerates the allowed event names, and scopes it to conversations originating from a Click-to-WhatsApp ad. No sibling tool sends conversion events, and an agent can distinguish it immediately from the wa_* messaging and template tools.

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 a clear precondition (the conversation must carry a captured ctwa_clid, 422 otherwise) and explains when to use test_code. It does not name an alternative tool, but no competing sibling exists, so the missing 'vs. X' element is minor.

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