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

Annotations already establish readOnly, idempotent, and non-destructive behavior. The description adds value by disclosing the exact return contents: the watch with post count and the 5 latest posts. It doesn't discuss error behavior for invalid IDs, but this is a minor gap given the simple retrieval semantics.

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 concise sentences with no filler. The primary return behavior is front-loaded, and the ID-discovery hint is placed immediately after, making the description efficient and easy to parse.

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 one-parameter read-only getter, this description is complete: it states what is returned, how to get a valid ID, and the annotations cover safety. No output schema is needed because the return contents are described directly.

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 0%, so the description carries the burden for parameter meaning. It clarifies that watchId is the identifier of a competitor watch and tells the agent where to obtain valid IDs, adding meaningful context beyond the schema's bare minLength string.

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 ('Returns') and resource ('competitor watch'), and specifies what it includes (post count and the 5 latest posts). This clearly distinguishes it from the many list and mutation sibling tools.

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?

It explicitly directs the agent to campaignstack_list_competitor_watches to find valid watch IDs, which is the main prerequisite. It doesn't specify when not to use this tool, but for a simple get-by-ID operation the guidance is clear and sufficient.

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