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

Beyond readOnlyHint=true, the description discloses the data provenance (INEGI) and, importantly, a paid-call model: '$0.001 USDC per call (x402)'. That cost and payment-mechanism detail is operationally significant and not present in annotations or schema. It stops short of describing response shape or rate limits, but the paid-access disclosure is the key behavior an agent needs.

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?

Two tight sentences: the resource and data granularity come first, the pricing caveat second. No filler, no restatement of the title. Slightly under-specified rather than over-long, so it is efficient but could afford one more clause on the year parameter.

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 one-parameter lookup with no output schema, the description covers source, granularity, effective-date semantics, and cost — enough to call it correctly. The absence of any return-format detail is acceptable given the stated fields, and the sole remaining gap (year range behavior) is covered by the schema.

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 the single 'anio' parameter already documents 'Year (default: current)'. The description adds nothing about the year argument — it doesn't clarify format, valid range, or how historical years are bounded. Baseline 3 applies when the schema carries the parameter burden.

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?

The description expands the opaque name 'uma' into 'UMA (Unidad de Medida y Actualización) values published by INEGI' and states the granularity (daily, monthly, annual with effective dates). An agent knows exactly what data comes back, though no sibling is named to differentiate it from other Mexican economic-indicator tools like iva or salario_minimo.

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?

There is no explicit when-to-use or when-not-to-use guidance, and no alternative tool is referenced. The only implicit signal is 'current and historical', which lets an agent infer the temporal scope but not the selection criteria against other indicator tools.

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