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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuine context beyond that: the units (percent per annum), the meaning of the series (key policy rate anchoring short-term peso borrowing), and the official government source. It stops short of return-shape or update-frequency detail, but that is captured by the output 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?

Front-loads the core purpose in the first sentence and uses later sentences for scope, units, and provenance. Slightly verbose with parentheticals (Tasa objetivo, serie SF61745, JOGI), but each element is informative rather than filler.

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 two-optional-parameter rate series with an output schema, the description covers identity, units, source, and latest-vs-range behavior. Return values are left to the output schema, which is appropriate. Nothing an agent needs to call the tool correctly 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%, with both optional dates fully documented in the schema itself (format, and 'omit for latest observation only'). The description restates the latest-vs-range behavior but adds no syntax or constraint beyond it, so the baseline of 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 (Get) and a precisely named resource (Banco de México monetary policy overnight target rate), including the SIE series ID SF61745 and the issuing body (JOGI). An agent can distinguish this from banxico.rates.tiie (a different reference rate) and the FX siblings without opening any 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?

'Returns the latest rate or a historical date range' implies how the tool is invoked but does not state when to prefer it over banxico.rates.tiie or a broader macro tool. No explicit when-not or alternative routing is provided, so usage is only weakly guided.

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