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

No annotations are provided, so the description carries the burden. It discloses the 10 MB limit and base64 encoding, which are useful behavioral constraints. However, it does not mention what happens on success/failure, whether the upload is permanent, or any side effects beyond binding to a channel.

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?

Two sentences with no wasted words. The core constraint (10 MB, base64, channel-bound) is front-loaded, and the routing hint is concise.

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 simple upload tool with 100% schema coverage, the description is mostly adequate. However, with no output schema and no annotations, it would benefit from stating what the response contains (e.g., attachment ID) and any authentication requirements beyond the connection parameter.

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 all parameters. The description adds context about the 10 MB limit and base64 format, which relates to the 'data' parameter, but does not add meaning beyond the schema for channel_id, name, or connection.

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 states a specific verb ('Upload'), a resource ('attachment'), and key constraints (up to 10 MB, base64, bound to a channel). It is clear enough to distinguish from siblings like message_send or channel_create, though it does not explicitly name a sibling alternative.

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 a clear usage hint: 'Prefer the HTTP upload endpoint for large files.' This implies when to use this tool (small files) and when to avoid it (large files), though it does not explicitly name the alternative endpoint or provide detailed conditions.

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