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

Annotations already declare destructiveHint=true, idempotentHint=true and openWorldHint=true, so the description's job is to add scope — and it does: it modifies stored audience/lists data only, performs an external ESP credential check, and consumes no credits. It does not say what happens on credential-validation failure or whether the call blocks until sync completes.

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 tight clauses, front-loaded with the action and immediately followed by the side-effect/cost caveat. Every phrase — credential re-validation, audience refresh, stored-data-only, no credits — carries information an agent needs.

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 2-parameter mutation with full schema coverage, full annotations and no output schema, the description covers action, target, side effect and cost. The only gap is error/return behavior on failed credential validation, which is minor given the annotation set.

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%: `id` is documented as 'Connection id.' and `type` as an ESP slug with a 42-value enum. The description's `{type}`/`{id}` path template restates the same semantics without adding format or edge-case guidance, 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?

The description gives a precise verb pair ('re-validate... and refresh') against a named resource ('a connection's stored credentials', 'audiences/lists') and even pins the endpoint POST /v1/integrations/{type}/connections/{id}/sync. It does not, however, distinguish itself from the sibling test_integration or disconnect_integration, which an agent would plausibly confuse it with.

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?

Usage is only implied: re-sync when credentials or audience data need refreshing. There is no explicit statement of when to call this instead of test_integration (validation only) or disconnect_integration, so the agent must infer the boundary.

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