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

Adds substantial behavior beyond the readOnly/idempotent annotations: the exact result vocabulary per step, the `done`/waiting polling contract, that subjects are matched but never returned, the `within` tolerance default, and the Labs-gating error behavior. This is exactly the context annotations cannot carry.

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?

One dense paragraph that is front-loaded with the core purpose before drilling into step semantics and the Labs caveat. Every sentence carries information, though the run-on parentheticals make it heavier than needed.

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 fully specifies the return shape (per-step status plus timing, and the `done` flag), the polling expectation, and the environment prerequisite. An agent has everything required to call it and interpret results.

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?

At 67% schema coverage the description meaningfully compensates: it explains `since` as the series start, what each step's fields mean (subject phrase, category, code/link, after, within), and supplies the `within` default (a tenth of `after`, min 10 minutes) that the schema omits.

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 and resource — checks a welcome series / drip campaign by expecting each step's email in order after `since`. It reads clearly as distinct from siblings like check_email or wait_for_code, which wait for a single message rather than verifying an ordered series.

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 clear operating context: steps answer pass/early/late/missing/waiting, and `done` is false while any step is waiting 'so call again later', plus the Labs prerequisite. It does not explicitly contrast with sibling alternatives (check_email, wait_for_code/link), so a 4 rather than a 5.

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