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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false, so the safety profile is covered; the description goes further by disclosing the credit cost (2 credits), the paid-plan gating of universal/locally administered decoding, and the paid-plan expansion into vendor/OUI lookup. Those are real behavioral constraints an agent cannot infer from the annotations or 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?

Three sentences, front-loaded with the core validate-and-convert behavior, then optional enrichments, then cost. The only waste is the redundant 'MAC Address Lookup: MAC Address Lookup' prefix; otherwise 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?

With an output schema present, the description does not need to enumerate return fields, and it still names the supported format families and the enrichment outputs. It stops short of describing failure behavior for a malformed MAC or whether all formats are returned at once, which are the remaining gaps for a validation tool.

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 the baseline is 3, but the description adds meaning the schema omits: that the universal vs locally administered split (and the vendor/OUI data) is plan-dependent, and that 'addressing' controls an enrichment branch rather than the base conversion. It does not add syntax guidance for the 'mac' parameter beyond the schema example.

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 ('validates any MAC address and converts it across standard colon, dash, dot, and raw hex formats') and layers two optional capabilities on top: address-type decoding and vendor/OUI lookup. This clearly distinguishes it from nearby identifier lookups such as USBVendorLookup, BluetoothCompanyLookup, and IPLookup.

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?

Gives conditional guidance for the optional path ('Add addressing=true to read whether it is unicast, multicast or broadcast') and flags that vendor/OUI data requires a paid plan. It does not explicitly state when to choose this over sibling lookups or what happens on invalid input, so it is context-rich but not a full when/when-not routing statement.

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