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

Annotations declare readOnlyHint=false, openWorldHint=true, destructiveHint=false. The description adds valuable behavioral context: it explains the return structure (object keyed by provider), the 'connected' boolean for telling users about unset integrations, and the special ALL_ACTIVE_USERS literal. It doesn't contradict annotations. It could mention that the tool may fail if the user belongs to multiple orgs and slug is omitted, but that's covered in the parameter description. The description goes beyond annotations by explaining the shape and semantics of the response.

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 well-structured and front-loaded with the core purpose. It includes a concrete example that illustrates the expected usage pattern. It's a bit long but every sentence earns its place: the return structure, the connected boolean, the email special cases, and the example all add necessary information. The example is particularly helpful for an agent to understand how to map user requests to channelId values.

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 list tool with one optional parameter and no output schema, the description is quite complete. It explains the return shape, the special email cases, and the relationship to sibling tools. It doesn't describe pagination or rate limits, but for a destination-listing tool that's likely not a concern. The description covers what an agent needs to know to call it correctly and interpret the response.

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 the schema already documents the slug parameter. The description adds context by explaining when slug matters (omit to auto-detect, fails if multiple orgs) and how it relates to the tool's behavior. It doesn't repeat the schema but adds a small amount of value. Baseline 3 is exceeded slightly because the description clarifies the failure mode and the auto-detection behavior.

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 clearly states the tool's purpose: listing every destination the organization can deliver reports or alerts to. It specifies the resource (destinations) and the verb (list), and distinguishes it from sibling tools like create_report and create_alert by explicitly saying to call it before those to resolve channelId values. The example further clarifies the intended use.

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 provides explicit when-to-use guidance: 'Call this before create_report or create_alert to resolve channelId values.' It also gives specific instructions for handling email recipients, including using destinations.email.self for 'email me' and asking the user for any other explicit recipient. This is clear, actionable guidance that an agent can follow without ambiguity.

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