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

readOnlyHint=true already covers the safety profile, so the description's job is to add context — which it does by explaining the provenance of entries (API, recipient STOP reply, BulkSMS) and the pagination contract. It stops short of auth requirements, rate limits, or return ordering, so it is not exhaustive.

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 with the core purpose front-loaded, followed by the paging rule and the endpoint mapping. Nothing is redundant and nothing reads as padding.

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 two-optional-parameter read-only list with no output schema, the description covers what is listed, where entries come from, and how to page. Minor gaps remain around returned fields and sort order, but an agent has enough to call it correctly.

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 coverage is 100%, so baseline is 3, but the description genuinely adds value: it explains the cursor pattern ('min_id = the largest id of the previous page + 1'), which the schema only states as a bare threshold. That is real operational semantics beyond the structured field.

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?

Specific verb (List) plus resource (blocked numbers), and it goes further by defining what a blocked number means — a number the account may not send to — and enumerating the three ways entries get there. An agent immediately understands the content and can distinguish it from bulksms_block_number or the other list tools.

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?

Usage is implied rather than stated: the agent can infer you call this to audit who cannot be messaged, and the paging instruction gives operational guidance. However, there is no explicit when-to-use statement, no mention of bulksms_block_number as the mutation counterpart, and no exclusions or prerequisites.

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