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

Annotations already declare readOnlyHint=true, so the agent knows this is a safe read. The description adds useful behavioral context: it lists both inbound and outbound messages, orders newest first, and uses cursor pagination, which goes beyond the annotation and helps set expectations.

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, information-dense sentence. It front-loads the action and resource, includes ordering and pagination behavior, and appends the API endpoint. No wasted words.

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 simple list tool with two well-documented parameters, a read-only annotation, and no output schema, the description covers the essential aspects: what is listed, scope, ordering, pagination mechanism, and API reference. It is sufficiently complete for an agent to select and invoke 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 description coverage is 100%, with clear descriptions for both 'limit' and 'starting_after'. The description's mention of 'cursor page' aligns with the pagination parameters but adds little meaning beyond the schema, so the baseline score of 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 the specific verb 'List' with a clear resource ('SMS messages'), scope ('for the workspace'), ordering ('newest first'), and pagination style ('cursor page'). It also notes both inbound and outbound, distinguishing it from single-message tools like bird_get_sms_message and other message-type listers.

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 description clearly implies this is the tool for paginated listing of SMS messages in the workspace, giving context like newest first and cursor-based paging. It does not explicitly name alternatives or exclusions, but the resource specificity makes the intended use clear relative to sibling tools.

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