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

Annotations already establish readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false. The description adds useful behavioral context beyond that: it returns screens/buttons/fields and explicitly opens nothing by itself. It does not describe the exact output shape or any limitations of the guide content, so it falls short of 5.

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 short and front-loads the resource and the key caveat that it only returns instructions. The phrase about ChatGPT, Claude, or any AI agent is somewhat promotional and not needed for tool selection. The API note is useful for justifying the browser handoff but could be placed more cleanly.

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 zero-parameter, no-output-schema guidance tool, the description covers the essential points: what it returns, that it has no side effects, and which tools perform the actual action. It does not specify session/authentication expectations for the Sendible Cloud Browser, but the overall context is sufficient for an agent to know when and how to use it.

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?

The tool takes no parameters, so there is no parameter semantics to explain. The description appropriately avoids inventing inputs. Baseline 4 applies for a zero-parameter tool.

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 identifies the resource and action area (Sendible inbox messages) and clarifies the actual behavior: it returns step-by-step instructions rather than performing the archive. It distinguishes itself from the cotlet_browser_* tools by explicitly saying it opens nothing by itself. The leading phrasing could still be read as an action, which keeps it from a 5.

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?

It clearly says to use this for step-by-step Sendible guidance and then perform the action with cotlet_browser_* tools in the user's Sendible Cloud Browser. That gives a concrete usage path and distinguishes it from direct browser automation. It does not spell out when not to use it beyond the implicit no-side-effects warning.

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