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

The annotations already declare readOnlyHint=true, covering the safety profile. The description adds useful cost/performance context ('Cheaper than listing') and notes the grouping behavior, but it does not disclose rate limits, auth requirements, or the exact return structure. With annotations handling the safety baseline, 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 tight sentences plus the API endpoint reference. The core purpose and the key differentiator (cheaper than listing) are front-loaded, and every sentence contributes value without repetition or filler.

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?

Given a simple count tool with four well-documented parameters, no required fields, and readOnlyHint annotations, the description is nearly complete. The main gap is that it does not describe the return shape (e.g., total count vs. grouped breakdowns), which would help for the groupBy case, but with no output schema this is a minor omission.

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 schema already documents all four parameters in detail. The description mentions grouping dimensions and filtering, which aligns with the schema but adds no new syntax, format, or edge-case information. Baseline 3 is appropriate 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?

The description uses a specific verb ('Count') and resource ('links'), states the scope (matching a filter, optionally grouped by domain, tag or folder), and distinguishes itself from the list operation ('Cheaper than listing when you only need totals'). An agent can tell this apart from dub_list_links 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?

It gives clear context for when to use this tool ('when you only need totals') and contrasts it with the alternative ('listing'), but it does not explicitly name the sibling tool (dub_list_links) or state exclusions. The guidance is sufficient for an agent to choose correctly.

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