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

Goes meaningfully beyond the annotations by disclosing the irreversible nature ('cannot be undone'), the merge resolution policy (conversations, events, strictest consent retained), and that it operates on all duplicate sets at once rather than a chosen subset. It does not mention permissions or volume/rate constraints, but the annotations already cover the destructive profile.

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, no filler, with the action and scope front-loaded and the irreversible warning placed last for emphasis. Every clause carries information.

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 parameters and no output schema, the description is nearly sufficient: it explains behavior, scope, merge policy, and irreversibility. Missing only what happens on failure or partial merges and whether any confirmation/dry-run path exists, which leaves a small gap for a destructive bulk mutation.

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?

Zero parameters, so there is nothing for the description to disambiguate; the baseline of 4 applies. The description correctly signals that no input is required because scope is implicit (all duplicate sets).

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 (merges) and resource (contacts sharing an email address), plus the exact scope: 'every set' rather than a caller-selected pair. This distinguishes it cleanly from list_merge_candidates, count_duplicate_contacts, and merge_conversations.

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?

The description implies when the tool applies (you have duplicates and want them consolidated) but never states prerequisites, exclusions, or the natural alternatives: list_merge_candidates / count_duplicate_contacts for inspection before committing. Usage is inferable but not guided, and the destructive bulk semantics deserve explicit caution framing.

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