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

The readOnlyHint annotation already covers the read-only safety profile. The description adds the 'previously sent' scope and lists filter dimensions, but it does not disclose pagination behavior, default filtering, or what happens when no filters are provided. That is acceptable given the annotation, but not additive beyond it.

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?

The description is a single front-loaded sentence with no wasted words. It states the operation first and then the relevant filter categories in a compact list.

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 14 optional parameters and no output schema, the one-sentence description plus schema is workable but not complete. Parameter semantics are covered, but the agent gets no information about the return shape, default behavior, or pagination beyond the cursor parameter description. It is viable for invocation but leaves meaningful gaps.

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 parameters are already documented. The description only loosely enumerates some filter dimensions and does not add meaning beyond the schema; it also omits some filters like list, event, messageId, traceId, archived, and enqueued_after. Baseline 3 is appropriate.

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 uses a specific verb and resource: 'List messages you've previously sent.' This clearly establishes the operation and scope. It does not explicitly call out sibling distinctions, but the plural 'messages' and 'previously sent' help separate it from get_message, get_message_history, and send_message.

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?

There is no guidance on when to use this tool versus alternatives like get_message, get_message_history, list_notifications, or send_message. The description states what it does but gives no exclusions, prerequisites, or selection criteria.

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