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

The annotations already communicate that this is a mutating but idempotent, non-destructive operation. The description adds the useful detail that a custom profile can be applied per tenant, but does not disclose anything about partial failures, existing associations, or what happens after the operation. No contradiction exists between text and annotations.

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 filler. The first states the core action and scope; the second adds the optional per-tenant profile behavior. Every word contributes useful 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?

For a two-parameter mutation with fully described schema fields and an idempotency annotation, the description covers the essential invocation context. The only nuance not addressed—such as behavior when the user already belongs to a tenant—is not necessary to make a correct first call.

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?

The schema already provides descriptions for both user_id and the tenants array, giving 100% coverage. The description's mention of a custom profile per tenant slightly reinforces the schema's 'Tenant-scoped profile overrides', but does not add substantial meaning beyond what the schema already states.

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?

The description uses a specific action ('Add a user to multiple tenants at once') and clearly distinguishes this tool from the single-tenant sibling add_user_to_tenant by emphasizing the bulk, multi-tenant nature. It also adds the per-tenant custom profile capability, which makes the purpose unmistakable.

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 this is the right choice when multiple tenants need to be handled in one call, but it does not explicitly name add_user_to_tenant as the alternative for single-tenant operations or state any exclusion criteria. An agent must infer the usage boundary from the tool name and wording.

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