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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds useful cost/latency context ('cheaper than listing') and the underlying endpoint, but says nothing about return format, grouping result shape, or 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?

Three compact sentences, front-loaded with the core purpose and zero filler; the cost rationale and endpoint reference are each a single clause.

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?

No output schema exists, but 'only need totals' plus the explicit grouping dimensions adequately convey the return shape for a count tool. Minor gap: no statement of whether an ungrouped call returns a single total by default.

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 all four parameters are already documented with their own descriptions including the groupBy enum. The description adds only a high-level restatement of the grouping dimensions; baseline 3 applies when the schema does the heavy lifting.

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?

States a specific verb (count) and resource (links) plus the filter/grouping scope, and explicitly contrasts itself with listing ('cheaper than listing when you only need totals'), which separates it from dub_list_links. An agent can pick it correctly without opening the schema.

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?

Gives a clear selection condition ('when you only need totals') and implicitly names the alternative (listing), but does not name dub_list_links or state when-not to use it (e.g., when full link records are required).

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