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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false, openWorldHint=true), so the bar is lower; the description still adds real value by disclosing the shape of the payload returned (a field inventory) where no output schema exists. It omits pagination/rate-limit behavior, but those are covered by the schema's page/limit params.

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 compact fragments, zero padding, with the resource scope and the returned field inventory front-loaded. It could be marginally better structured as a sentence, but nothing wastes the agent's attention.

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 read-only, filter-and-paginate list endpoint with a fully documented parameter schema but no output schema, the description covers the missing piece (what fields come back). The only gap is the absence of explicit routing guidance to sibling list/segment/tag contact tools.

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 80%, so the schema already documents from/to/page/limit with formats and defaults. The description adds only the list scoping implied by 'on one list' and no extra syntax or semantics beyond that; 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 states a specific verb+resource scope: contacts belonging to one list, and enumerates the returned fields (email, name, phone, subscription state, tags, custom fields, LTV). 'On one list' is enough to separate it from bulk-list siblings like sendlane_list_contacts and tag/segment variants, though it never names those alternatives explicitly.

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?

Scope is implied by 'on one list', which hints that this is the list-scoped counterpart to a global contacts listing, but there is no explicit when-to-use/when-not statement and no named alternative among sendlane_list_contacts, sendlane_list_segment_contacts, sendlane_list_tag_contacts, or sendlane_list_list_unsubscribed.

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