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

With no annotations, the description carries the behavioral burden. It discloses the authentication requirement, the account-scoped read behavior, and the return organization ('by channel and message type'). It does not explicitly state read-only-ness, but 'List' strongly implies a non-mutating operation.

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 compact and front-loaded: it states the core purpose first, then the return format, then essential access instructions. Every sentence earns its place, and the access note is directly actionable.

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 read-only listing tool with no output schema, the description covers everything needed to invoke it correctly: what it returns, authentication requirements, and the fact that start_login does not authorize it. It also sets correct expectations about the data scope.

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 the schema is empty, so there is nothing for the description to clarify. Per the baseline for 0-param tools, this is adequate without additional parameter detail.

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 all custom message templates for the authenticated account.' The 'custom' qualifier distinguishes it from default templates, and the scope ('for the authenticated account') is precise. This clearly differentiates it from related siblings like get_template and get_default_templates.

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?

Provides explicit access prerequisites and a clear when-not: 'start_login does NOT open this tool.' It tells the agent to authenticate first and retry after doing so. It does not name alternative listing tools, but the auth warning is strong, actionable guidance.

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