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

Annotations already declare destructiveHint=true, readOnlyHint=false, idempotentHint=false and openWorldHint=true, so the safety profile is covered. The description adds a real behavioral fact in the master API key requirement, but it never explains the destructive effect itself — that existing owner assignments are overwritten — which is the key unknown for an agent calling a destructive bulk mutation.

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?

The functional sentence and the auth requirement are front-loaded in two short sentences with no redundancy. The injected pricing block is mandated boilerplate rather than authorial waste, but it does dilute the signal slightly.

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 annotations covering safety and an output schema covering the response, the definition is broadly serviceable. It is still thin for a destructive bulk mutation: no guidance on partial failure, batch limits, or what happens to the previous owner.

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 parameters carry descriptions, so the schema fully documents owner_id and contact_ids. The description contributes no additional parameter meaning (no ID format, no batch size ceiling, no behavior for invalid IDs), so the baseline 3 applies.

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+scope: reassigning a contact owner across multiple contacts, which implicitly separates it from the single-record patch_apollo_contacts_contact_id and from post_apollo_contacts_update_stages. It does not explicitly name those siblings, so differentiation is inferred from the 'multiple contacts' scope rather than stated.

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 prerequisite 'Requires a master API key' is a genuine usage constraint that helps an agent decide whether the call is even possible. However, there is no indication of when to prefer this bulk tool over the single-contact patch, nor any exclusion or limit guidance for the contact_ids set.

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