List Transactional Emails

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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and closed-world, so the safety profile is fully covered. The description adds domain context (what counts as transactional) and a display guideline about not surfacing ids/timestamps, but says nothing about pagination behavior or result volume. Adds some value over annotations without being rich.

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, front-loaded with the purpose before the disambiguation and the display note. The final sentence about not echoing ids/timestamps is response-presentation guidance rather than invocation guidance, but it is brief and non-redundant.

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 read-only, zero-required-parameter list tool with full param coverage and closed-world annotations, the description supplies the one thing the structured fields cannot: the definition of 'transactional' that separates this from the campaign siblings. Nothing critical is missing, though a pointer to the campaign alternative would make it 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 100%, so the cursor parameters (after/before, and the mutual-exclusion rule) and the limit range are already fully documented in the schema. The description contributes no additional parameter meaning, making the baseline 3 correct.

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 ('List transactional emails') plus what the listing contains ('with their delivery status'). It also disambiguates the resource type from the sibling family of campaign listers ('not campaigns'), so an agent can pick this over list-email-campaigns 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?

Clearly delimits the resource ('one-off sends ... receipts, one-time passwords, not campaigns'), which is exactly the condition separating it from list-email-campaigns and list-sms-messages. It stops short of naming the alternative sibling explicitly, so it does not reach full when-to-use/when-not routing, but the context is unambiguous.

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