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

Annotations already declare the read-only, idempotent, non-destructive profile, but the description adds genuinely new operational facts: no credit cost, no parameters, API key required, results scoped to the caller's account, and that an empty result means no lists exist. The only gap is return shape, which is unaddressed and there is no output schema.

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?

Front-loads the purpose and then layers usage, cost, and scope in short sentences. The parenthetical about locally stored leads is slightly convoluted but earns its place by preventing confusion with list_leads.

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 zero-parameter, read-only list tool with no output schema, the description covers everything an agent needs: auth requirement, cost, scope, empty-result meaning, and the sibling it should pair with. Nothing material is missing.

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 tool takes zero parameters, which is the baseline-4 case; the description correctly states 'takes no parameters' so an agent will not hunt for filters. It adds no further parameter detail, but none is needed.

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 the managed lead lists this account has created or synced') and explicitly scopes it to account-owned lists. It also distinguishes itself from the similarly-named sibling list_leads by noting the local corpus is shown there instead.

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 concrete when-to-use triggers tied to named siblings: find a listId before sync_lead_list, or check existence before create_lead_list to avoid a duplicate. It also names the alternative for raw leads (list_leads), so the agent can route without inference.

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