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

Beyond the readOnly/non-destructive annotations, it discloses a hard behavioral constraint an agent must respect: one call every 3 minutes, 429 otherwise. It also clarifies the filtering semantics (error events only) and the underlying endpoint, which annotations cannot convey.

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 tight sentences: purpose first, then the error-only constraint, then the rate limit. The trailing endpoint string is slightly tacked-on but each sentence carries operational value with no filler.

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 no output schema, the description compensates by naming the returned fields (recipient, source_docid, reason, orgtoken, timestamp) and stating that only error events appear. Combined with the rate-limit warning, an agent has everything needed to call this correctly and interpret the reply.

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%, so start/end/limit/offset are already fully documented, and the description only alludes to the window ('between two moments'). The field list (recipient, source_docid, reason, orgtoken, timestamp) describes return values, not parameters, so it adds no parameter meaning beyond 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 ('Email and SMS delivery problems ... for signing invitations') and enumerates the exact error reasons returned (hard_bounce, soft_bounce, blocked, spam, invalid_email, deferred). No sibling tool covers notification errors, and the explicit reason list makes the scope unmistakable.

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?

'Only error events are reported' tells the agent what this will and will not return, and the bounded window ('between two moments') plus the 3-minute rate limit defines when it can be called. It stops short of naming an alternative tool or an explicit when-not-to-use condition, but no sibling overlaps this behavior.

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