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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered; the description adds value by disclosing that results are personal data (email, phone, custom fields) and that the call maps to a GET endpoint, confirming a non-mutating server-side filter. It says nothing about pagination behavior or result volume limits, which the schema only hints at via next_offset.

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 short clauses with zero padding: resource and returned fields first, then the filter options, then the endpoint. Nothing is repeated from the schema and every sentence carries information.

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 an eight-parameter read with no output schema, the description usefully characterises the returned record shape and the available filters. The remaining gap is pagination and default result size, which the agent must infer from the offset/limit descriptions rather than from the tool description.

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 100%, so every one of the eight parameters is documented in the schema itself. The description only summarises the filter axes (email, phone, search, modified dates) without adding syntax, precedence, or combination rules, so the baseline of 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?

States a specific resource (contacts of one list) and what comes back (email, phone, custom fields), plus the underlying GET path, so it is clearly a filtered read of list membership rather than a write like sarbacane_create_contact. It does not explicitly distinguish itself from near-neighbours such as sarbacane_list_campaign_recipients or sarbacane_list_blacklist_entries, so sibling differentiation is left implicit.

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 filter dimensions (email, phone, text search, modification date) imply the lookup use cases, but there is no explicit when-to-use or when-not-to-use statement. Nothing tells the agent to call sarbacane_list_lists first to obtain list_id, or which sibling to prefer for recipient/blacklist lookups.

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