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

Annotations already declare readOnly/idempotent/non-destructive, so the safety burden is covered. The description adds real behavioral context beyond that: default ordering by most recent activity, that `email` overrides all other filters, and that the timeline is capped at `limit`. It doesn't mention pagination behavior of `offset` or the shape of a list-mode result, keeping it from a 5.

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?

Three compact sentences, front-loaded with the core capability, followed by filters and then the special email mode. The paraphrased example ('tell me everything we know about Sarah') earns its space by disambiguating intent. No filler.

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?

There is no output schema, but the description covers the return shape for the email mode (contact record plus timeline, newest first, up to `limit`). The list-mode row shape isn't described, which is the main gap for a 9-parameter listing tool. Otherwise an agent has enough to call it correctly.

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 only 11%, so the description has to carry the load, and it does: it names the filter axes (text, tags, activity thresholds) and maps them to `min_submissions`, `subscribed_only`, and `since`. The `email` mode's override semantics ('the other filters are ignored') are also stated in prose. `limit` and `offset` paging semantics are left to the schema defaults.

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 ('List contacts who have interacted with a site') and scopes it with concrete qualifiers (filled a form, subscribed to newsletter). This clearly separates it from sibling tools like list_submissions and read_submission, which operate on individual form entries rather than contacts.

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?

Explicitly says which filters to use for list queries and dedicates a sentence to the alternate mode: 'Pass `email` for everything about one person.' The when-to-use for the single-person lookup is concrete and even includes a natural-language example. It stops short of naming sibling alternatives such as list_submissions, so it's not a 5.

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