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

No annotations are provided, so the description carries the full disclosure burden. It implies a read-only lookup, but says nothing about behavior on a missing ID, permission or scope requirements, rate limits, or whether data is cached, so the agent must discover failure modes by trial.

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 actual purpose is front-loaded in a single, tight sentence. However, the trailing HTTP status block ('200: Successful Response, Content-Type: application/json') is boilerplate that conveys no actionable information and dilutes the definition.

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 two-parameter getter with no annotations and no output schema, the description establishes what is returned only generically ('a specific IM message') and never describes the response shape. It is minimally adequate but leaves the agent guessing about the not-found case and platform expectations.

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 baseline is 3, but the schema's own descriptions are tautological ('Platform', 'Message ID') and the tool description adds nothing beyond 'unique ID'. It does not clarify accepted platform values or ID formatting.

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 ('Retrieve') and resource ('a specific IM message') and qualifies the lookup key as 'its unique ID', which distinguishes it in kind from the search_im_messages sibling. It does not explicitly name any sibling, so it stops short of a 5.

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?

There is no explicit when-to-use guidance, no statement of prerequisites (e.g., that you must already have a message ID), and no routing to alternatives such as search_im_messages when only partial details are known. The 'by its unique ID' phrasing implies usage but never states when not to use it.

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