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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description usefully adds ordering ('newest first') and pagination model ('cursor page'), but says nothing about result fields, rate limits, or what happens when the workspace has no messages.

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 with the ordering and pagination semantics front-loaded and an endpoint reference tacked on for orientation. Nothing redundant or padded.

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 no output schema, the description covers pagination mechanics but not the shape of a returned message or how next_cursor surfaces in the response. Adequate but leaves the agent to infer the return contract.

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 both limit and starting_after are already documented in the schema; the description only echoes the cursor concept. Baseline 3 applies when the schema does the heavy lifting.

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 email messages') plus scope ('sent from the workspace'), which separates it from bird_get_email_message and the SMS/WhatsApp list siblings. It does not explicitly name those siblings, but the resource noun is unambiguous.

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 by the list-vs-get naming and by the cursor/ordering note, but the description gives no explicit when-to-use guidance, no preconditions, and does not point to bird_get_email_message for fetching a single message.

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