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

readOnlyHint=true and openWorldHint=false already establish this as a safe, closed-world read. The description adds useful framing ('the only products orderable through this server', plans include merchant-verification links), but says nothing about pagination, caching, or freshness of pricing data, so it stays at the lower bar set by the annotations.

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 action and result contents. Every sentence carries information (contents, use trigger, scope/exclusion), though the final May sentence is somewhat tangential to listing plans.

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 a no-parameter read tool with no output schema, the description adequately previews the returned fields (pricing, inclusions, scope, delivery, guarantee, links) and the domain boundary. Only the lack of any count/format expectations keeps it from full completeness.

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?

The tool takes no parameters and the schema coverage is 100%, so there is nothing for the description to disambiguate. Baseline 4 applies for a zero-parameter tool.

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?

Specific verb and resource ('List Mako Metrics plans') followed by an enumeration of what the listing contains: pricing, inclusions, scope limits, delivery, guarantee, and merchant-verification links. This is enough to distinguish it from siblings like order_report or list_deliverables 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?

'Use this to recommend a plan before ordering' gives a clear trigger point. It also scopes the tool ('competitor report plans... the only products orderable through this server') and routes the May agent engagement out to makometrics.com/meta-ads-agent, but it does not name a sibling tool as a direct alternative, so it stops short of the top tier.

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