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

Annotations already flag destructiveHint=true and non-idempotency; the description adds real value beyond that by disclosing that delete is a soft delete, that merge folds duplicates in and then deletes the merged ids, and that both require confirmation. That is exactly the behavior context an agent needs before mutating data.

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?

A single dense sentence, front-loaded with the overall purpose, then action-by-action clauses. No filler; every clause carries a rule or constraint.

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 17-parameter, nested-object dispatcher with no output schema, the description covers the action model and the highest-risk semantics (delete/merge confirmation, soft delete, restore source). It's close to complete; only a note on return format or per-action failure behavior would round it out.

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 94%, so the schema already documents nearly every parameter. The description mostly restates schema facts (firstName required for create, tags by name, keepId/mergeIds roles, set fields) rather than adding syntax or edge-case meaning, so baseline 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+resource ('Change contacts') and then concretely delineates each of the six actions. It references the sibling contacts_list contextually ('ids from contacts_list deleted'), but never draws a clean line between managing versus listing — a small gap against a 5.

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?

Gives actionable conditions per action: confirm before delete, confirm before merge, restore using ids from contacts_list deleted. It tells the agent how to pick an action but doesn't state any when-not to use, or route to siblings like contacts_list/tags_manage.

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