list_external_channel_messages

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

The description adds significant context beyond the readOnlyHint annotation by detailing the unsupported-provider behavior (supported=false, unsupportedReason, empty array) and explicitly stating the tool never sends, replies, deletes, mutates, or returns fake messages. No contradiction with 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, front-loaded with the core purpose, and every sentence adds necessary information. No redundant or filler content.

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?

Given that an output schema exists, the description adequately covers the key behavioral aspects: read-only nature, provider-specific behavior, and explicit guarantee against mutations. The unsupported case is well-documented. Complete for a list tool with good annotations and schema.

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 coverage is 100%, but the description adds meaning by stating channel can be specified by name or ID (schema only says 'string that will be trimmed'). The limit defaults and cap are also mentioned, though present in schema too. Overall, value-added beyond schema.

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 uses a specific verb ('List') and resource ('read-only messages for an external Gmail or Telegram channel'), clearly distinguishing it from sibling tools like list_channel_messages which handle internal channels. The scope and providers are explicitly named.

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 implies usage for external channels (Gmail/Telegram) but does not explicitly state when not to use it or list alternatives like list_channel_messages for internal channels. The behavior for unsupported providers is detailed, but usage guidance remains implicit.

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