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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds the 30-day cycle rotation and the three-part content shape (value, meaning, commitment), which is worthwhile context. It says nothing about invalid dates or out-of-cycle behavior, so it is useful but not rich.

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 short clauses that front-load the resource and its contents. The bilingual ES restatement is redundant for an agent but brief enough not to obscure the English original.

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 zero-required-parameter read-only lookup with a fully documented schema and complete annotations, the description covers the essentials and hints at the return shape. The missing piece is sibling disambiguation against values_for_agents, which a routing agent genuinely needs.

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% — the date pattern, the Europe/Berlin default and the language enum are all documented in the schema. The description adds no parameter meaning, so the baseline 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?

The description identifies the payload concretely — a day's value from a 30-day cycle plus its meaning for agents and a concrete commitment — so an agent knows roughly what comes back. But there is no verb phrase and no differentiation from the sibling values_for_agents, so the agent cannot tell from the text alone whether this is the same catalog or a different resource.

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 guidance on when to call this versus values_for_agents, saint_of_the_day, or readings_of_the_day, and no note that the cycle rotates every 30 days in a way that affects repeat calls. The agent must infer usage entirely from the tool name.

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