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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered structurally. The description adds value beyond that by disclosing the return format ('as a single number'), which matters because no output schema exists. It stops short of noting account-scope caveats or what zero/disabled contacts are counted, so it is not fully 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, zero waste. The core behavior and return shape are front-loaded, with the sibling routing placed 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 parameterless read that returns a scalar, the description supplies everything needed: what it returns, how it is shaped, and when to prefer the richer overview tool. With no output schema present, the return-value statement fills exactly the gap that would otherwise exist.

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?

The tool takes zero parameters, so the baseline is 4 and there is nothing for the description to disambiguate. No parameter semantics are needed or missing.

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 and resource ('Return the total number of contacts in the account') plus the exact return shape ('a single number'). It then explicitly names the sibling tool it is not, so an agent can distinguish it from directiq_account_overview without opening either 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?

Names the condition for using this tool ('a quick count') and the condition that selects the alternative ('counts plus active/disabled status, lists, tags, and senders' → directiq_account_overview). Both the when and the alternative are stated outright.

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