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

Annotations already declare readOnlyHint=true, openWorldHint=true, destructiveHint=false, so safety is covered. The description adds the underlying endpoint and the shape of the returned fields, but says nothing about auth, pagination, or rate limits.

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?

One dense sentence that front-loads the verb and resource, then the useful cross-reference to consuming tools. Every clause earns its place, though the parenthetical example list is slightly redundant with the enumerated fields.

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?

With no output schema, the description usefully tells the agent what fields come back and what the user_tag is for, which is exactly the missing piece. Minor gap: it doesn't clarify when to set include_all, leaving that entirely to the schema.

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% and the single parameter include_all is fully documented in the schema, so the schema does the heavy lifting. The description never mentions include_all or what 'hidden from public sign-up forms' means, so it adds nothing beyond the schema. Baseline 3 applies.

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?

Specific verb (List) plus resource (contact data fields), and it enumerates the returned attributes (id, label, type, required flag, user_tag). It also names the sibling tools that consume the user_tag key, making it distinguishable from list/contact tools in the sibling set.

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?

Implies its role as a discovery step by stating that robly_subscribe_contact and robly_update_contact use the returned user_tag as the field key. No explicit 'when not to use' or prerequisite ordering is given, but the context is clear.

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