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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, so the safety profile is fully covered by structured data. The description adds the enumeration of possible status values, but it does not disclose pagination behavior, result ordering, or what happens when no domains match. Given the strong annotation coverage, this is a modest contribution.

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, zero filler, and the core capability is front-loaded ahead of the filtering detail. Every clause carries information an agent can act on.

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 list tool with four optional, fully documented parameters and no output schema, the description covers purpose and filtering adequately while annotations carry the safety and idempotency profile. A small gap remains around result shape and pagination totals, but nothing an agent needs to invoke it correctly is missing.

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 page, limit, search and status are all documented in the schema including the enum and defaults. The description only restates that filtering by status and searching by name exist, adding no syntax, format, or matching semantics beyond the schema. Baseline 3 applies.

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 sending domains") and names the attribute set being returned (authentication status with its three values). An agent can immediately distinguish it from a single-domain reader like get_domain, though the description never names the siblings it differs from.

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?

The second sentence implies when the filters are useful ("Filter by status or search by name"), which gives some usage context. However, there is no explicit when-to-use/when-not guidance relative to get_domain for a single domain or add_domain for creation, so the routing is left partly to inference.

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