messente_lookup_numbersNumber lookup (HLR): is each number valid, ported, roaming, and which network it is on. COSTS CREDITS: Messente charges per number looked up (EUR 0.002 per number in its docs) and the Number Lookup service must be enabled on the account (a fixed monthly fee applies per Messente's docs). Up to 10 numbers per call. Messente: POST /hlr/sync.
| Name | Required | Description | Default |
|---|---|---|---|
| numbers | Yes | Phone numbers in E.164 format (1-10). |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations declare readOnlyHint=false without saying why; the description fills that gap by disclosing per-lookup credit charges (EUR 0.002) and the required account service. It also documents the 10-numbers-per-call ceiling and the underlying endpoint. It does not explain why the tool is flagged non-read-only (balance mutation) in so many words, keeping this short of a 5.
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 tight, front-loaded sentences: purpose first, then cost/prerequisite constraints, then the call limit. Every element is useful, though the trailing 'Messente: POST /hlr/sync.' endpoint note is the one item an agent does not strictly need to invoke the tool.
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 compensates by naming the data points returned (valid, ported, roaming, network) plus cost and volume constraints. It stops short of describing response shape or failure behavior for invalid numbers, but nothing essential for a correct call 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?
Schema description coverage is 100% and there is a single parameter, so the E.164 pattern and min/max items are already fully documented structurally. The description restates the 10-number limit but adds no format or syntax detail beyond the schema, making 3 the baseline.
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 and then enumerates exactly what the lookup returns: validity, portability, roaming status, and network. This is far more specific than its siblings (blacklist, balance, SMS, statistics) and lets an agent pick it without opening the schema.
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?
It gives a real prerequisite (the Number Lookup service must be enabled, with a monthly fee) and a cost cue that steers usage decisions, but it never states when NOT to use it or points to an alternative sibling for related needs. Usage context is implied through cost and enablement rather than explicitly framed.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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