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

Annotations already indicate readOnlyHint=true and destructiveHint=false, and the description goes further by revealing that health and recent failure state are included. Most importantly, it discloses that connection settings such as URLs and tokens are never returned, a privacy-relevant behavioral trait not present in structured data. This is valuable transparency beyond the annotations.

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 two sentences with no filler. The first sentence conveys the core function and return content, and the second adds a critical privacy caveat. Every phrase earns its place and the most important information is front-loaded.

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 no-parameter listing tool with an output schema, annotations covering safety, and clear read-only semantics, the description is complete. It tells the agent what will be returned, what will not be returned, and what health information is available. No important calling context 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?

The tool has zero parameters and an empty input schema, so there is nothing for the description to add about parameter semantics. Per the zero-parameter baseline, this is a 4; the description correctly focuses on behavior rather than inventing parameter guidance.

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 names a specific verb ('List'), the resource ('destinations'), and the scope ('where your signals are delivered'), making the tool's function immediately clear. It also distinguishes itself from sibling create/update destination tools by emphasizing read behavior and from list_sources/list_signals by focusing on destinations. The added detail about health and failure state sharpens the purpose beyond just a generic list.

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 gives clear context for when this tool is useful: when an agent needs to see delivery destinations and their health/failure status. It does not explicitly state when not to use it or name alternatives, but the read-only framing and the privacy caveat implicitly guide an agent away from expecting destination creation or credential access. This is solid contextual guidance without explicit exclusions.

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