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

Annotations already declare idempotentHint=true, destructiveHint=false and readOnlyHint=false, so the safety profile is partly covered. The description adds a scoping nuance about effects on other clients, but that sentence is ambiguously worded ('not affected by merely listing') and leaves the actual mutation/visibility scope unclear.

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 short sentences with no padding and the core action front-loaded. The second sentence, however, is confusing rather than clarifying, so it does not fully earn 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?

An output schema exists so return values need not be described. Still missing for a mutation tool with a 100-item batch limit: partial-failure behavior, whether ack is per-user or per-client, and how it differs from dismiss_address_book_match.

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 50%: idempotency_key is documented inline, but match_ids (array of UUIDs, max 100) has no inline description. The tool description adds nothing about match_ids semantics, batching limits, or what happens to already-seen IDs.

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 (marks as seen) and resource (address book matches) with the observable outcome ('so they stop appearing as new'). It does not distinguish itself from the sibling dismiss_address_book_match, which an agent could easily confuse with this tool.

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?

No when-to-use guidance, no prerequisites, and no mention of the closest alternatives (dismiss_address_book_match, list_address_book_matches). The second sentence is a behavioral note, not a usage rule, so the agent must infer the trigger context.

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