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

Annotations already declare readOnlyHint/idempotentHint/destructiveHint=false, so the closing 'Read-only' is largely redundant. What the description adds beyond annotations is genuinely useful: the exact privacy boundary (no member names, comments, files, invitations, secret tasks) and the provenance warning that item texts are written by list members, which signals untrusted content. It does not cover return ordering or empty-list behavior.

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 two-mode behavior is front-loaded in the first sentence before the exclusion list, and every clause carries information. The field enumeration ('title, note, date, priority, done') is dense but earns its place given there is no output schema.

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 takes responsibility for describing return values in both modes (role and counts; title, note, date, priority, done, assignment) and caps the scope with the exclusion list. An agent can call this correctly and predict the shape of the response without further help.

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 0% and the single parameter has no description at all, so the description carries the burden — and it does: it states that list_id switches the tool from list-summary mode to single-list item mode. It does not explain the required ID format (only the JSON Schema pattern hints at 's-' prefixed hex), so a small gap remains.

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?

Opens with a specific verb and resource ('Returns the user's shared lists') and immediately names the domain concept ('the Together lists in the Zarok app') an agent may be searching for. It also distinguishes the two result shapes and scopes what is excluded, so it is clearly separable from siblings like zarok_add_shared_list_item or zarok_set_shared_list_item_done.

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 when-to-use split is explicit: omit list_id to get the list of lists with roles and counts, supply list_id to get that list's items. There is no explicit exclusion naming a sibling alternative or a stated precondition, which keeps it just short of a 5.

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