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

Annotations already establish readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds genuinely useful context beyond that: the output describes a hypothetical mutation, and this is "the only place the outcome is visible while it is still reversible by not acting" — clarifying the tool's role as a pre-commit inspection step.

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?

Front-loaded with the core promise ("Everything a merge of this group would do, before it happens") followed by a comma-separated enumeration and a single justification sentence. Slightly dense, but every clause carries information and nothing is wasted.

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 output schema, the description carries the burden of explaining return values — and it does so thoroughly, listing exactly what the agent will see. Combined with the annotation-covered safety profile and the schema-documented params, nothing needed to call or interpret this tool is missing.

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 coverage is 100% and both required parameters (group_id, connection_id) are documented in the schema, including the prerequisite calls list_duplicate_groups and list_crm_connections. The description adds nothing about parameters, so the baseline of 3 is appropriate.

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-like action (dry-run preview of a merge) on a specific resource (this duplicate group), and enumerates exactly what the result contains: survivor, absorbed records, resolved field values with provenance, archived values, and match rationale. This clearly separates it from approve_duplicate_group and reverse_duplicate_group.

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?

"Read this before approving anything" gives clear contextual usage and ties the tool to the approval workflow, implicitly routing the agent to approve_duplicate_group. It does not name a sibling explicitly or state when not to use it, so it falls just short of the 5 bar.

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