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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is fully covered. The description adds the concrete endpoint (GET /api/customers.json) and the returned field surface, which is useful but not a deep behavioral disclosure; pagination defaults live only in the 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?

A single compact sentence that front-loads the action and resource, then closes with the raw endpoint. 'contacts (customers)' is slight redundancy but useful name-mapping rather than waste.

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's field enumeration (name, phone, email, tags, notes, custom fields, consent, reachability) usefully signals what comes back. Pagination and search semantics are adequately handled by the schema, leaving little an agent would still need.

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 100% – page, query, and page_size all carry their own descriptions including defaults and max values. The description contributes nothing about parameters, so the 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?

States a specific verb pair and resource ('List or search contacts (customers)') and even disambiguates the colloquial vs API naming. It enumerates the address-book fields covered, so an agent can distinguish it from textline_get_customer, but it never names the sibling retrieval tools 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?

The 'list or search' phrasing implies the browse/filter use case, but there is no explicit when-to-use guidance against textline_get_customer, textline_get_customer_by_phone, or textline_list_saved_searches. No exclusions or preconditions are stated; usage must be inferred from the name and siblings.

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