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

With no annotations provided, the description carries the behavioral burden. It does disclose a read-like retrieval action and an author-inclusion behavior, but it says nothing about not-found handling, permissions, or response shape. For a simple fetch this is adequate but not rich.

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 filler, deeply front-loaded: the core purpose appears first, and the sibling routing appears second. Every clause earns its place.

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 single-parameter fetch tool, the description plus schema covers the essential invocation context: what to fetch, how to identify it, and how to get replies. A small gap remains around not-found behavior and what the full returned discussion object contains, but overall it is sufficient for an agent to select and call the tool.

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%, so the schema already documents the sole parameter, including its UUID format and source (from list_discussions). The description's 'by uuid' adds no meaning beyond the schema, so the baseline of 3 is appropriate.

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 clearly identifies the action ('Fetch'), the resource ('one discussion'), and the lookup key ('by uuid'). It also distinguishes this from list-style siblings by scope, and the phrase 'with author' adds a specific return expectation.

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 second sentence explicitly directs the agent to the appropriate alternative: 'Use list_discussion_replies for its replies.' This tells the agent when to use a sibling instead, which is clear, actionable guidance.

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