add_attachments_to_message

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

Annotations already mark the tool as not read-only and not destructive; the description adds that it consumes supplied links and returns a confirmation with resulting attachments. It does not go into duplicate handling or URL validation, but it gives enough behavioral context for normal use.

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 front-loaded with the one-sentence purpose and then uses compact labeled sections for condition, alternative, prerequisite, example, and return. No filler.

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 two-parameter mutation with no output schema, the description covers the call prerequisites, example payload, and a return expectation. It leaves the return shape vague as {...}, but this is adequate for a confirmation-style 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?

The schema describes links but leaves id as a bare string; the description fills that gap by pointing to list_messages results[].id. The example also anchors both parameters with concrete values.

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 opening sentence names a specific action and resource: attach one or more link URLs to an existing message. The USE INSTEAD note explicitly separates it from create_message_share_link by contrasting producing a link vs consuming them.

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?

USE WHEN states the intended trigger, USE INSTEAD names the sibling not to choose and why, and FIRST gives the prerequisite call to list_messages for the id. This removes ambiguity about when and how to invoke the tool.

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