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

Beyond the readOnlyHint/openWorldHint annotations, the description discloses a genuinely important behavioral trait: the API returns the entire list while this tool truncates to the first `limit` numbers and reports the total count, so the agent knows results are partial and paging may be required. It also exposes the underlying endpoint (POST /api/crm), which explains why a read appears as a POST. Return shape detail beyond 'total count' is not given.

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 key behavior — truncation to limit plus total count — is front-loaded in the first two sentences. The trailing REST note ('POST /api/crm with Action details') is terse and slightly cryptic but short enough not to bloat the definition.

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 carries the burden of describing returns and does so adequately: a set of mobile numbers plus a total count. Combined with fully documented parameters and read-only annotations, an agent has enough to invoke it correctly, though it doesn't describe the shape of each entry or how paging terminates.

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%, so all three parameters are already documented, including offset paging via next_offset. The description reinforces limit semantics ('first `limit` numbers') and that a total count comes back, but says nothing about offset, which is the parameter an agent is most likely to misuse. 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 and resource: 'Show the mobile numbers stored in one list,' which is clearly distinguishable from the sibling smseveryone_list_contact_lists (which returns lists, not numbers). It stops short of explicitly naming that sibling as the contrast, but the resource scope is unambiguous.

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?

Usage is only implied: the agent must infer that this is the tool to call once it has a CrmId, and that inference is carried by the list_id parameter description referencing list_contact_lists rather than by the prose. No explicit when-to-use, when-not-to-use, or alternative is stated in the description.

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