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

Annotations already declare readOnlyHint=true, so safety is covered. The description adds useful ordering behavior ('newest first') and identifies the underlying REST endpoint, but says nothing about pagination behavior despite the iterator parameter existing.

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?

Two short sentences, front-loaded with the core purpose, with a useful usage tip second. The REST path is arguably redundant but is compact and aids precision.

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 listing tool with fully documented parameters and annotations covering the safety profile, this is nearly complete. The only gap is pagination behavior, which the iterator parameter implies but the description does not confirm.

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 all six parameters are already documented, including the status code mapping and limit defaults. The description adds only a hint that the status filter surfaces failures; it does not explain iterator usage or status_code_class semantics beyond the schema. 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?

States a specific verb (List), resource (delivery attempts), and scope (against one endpoint, newest first). The scoping phrase distinguishes it from the sibling svix_list_attempts_by_message without needing the 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?

'Filter by status to find the failures' gives one implied usage pattern, which is helpful. However, no alternatives are named and there is no when-not guidance (e.g., when to use list_attempts_by_message instead).

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