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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is known. The description adds useful context about what the response contains (keynote, guidance, direction), but does not describe behavior such as language fallback or how invalid IDs are handled. The description does not contradict 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?

Two tight sentences with no filler. The main action and scope are front-loaded, then the content is listed, and the intended use cases close it out. Every sentence earns its place.

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 read-only single-resource lookup with fully documented parameters and safe annotations, the description covers the essential behavior and output contents. There is no output schema, but the listed fields give a reasonable preview. It does not mention error cases or language fallback, but the schema covers lang defaults well enough.

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%, so the input schema already thoroughly documents id, lang, and compact with enums, defaults, and examples. The description does not need to repeat parameter details. It adds no additional meaning beyond the schema, matching the baseline for full schema coverage.

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 uses a specific verb and resource: 'Retrieve the full profile of one tonalpohualli day sign' and enumerates the delivered content (Nahuatl name, meaning, direction, keynote, guidance). It also clearly distinguishes this singular-resource tool from the plural sibling by emphasizing 'one' and 'single Mexica sign,' plus the stated use case of detail pages and single-sign chatbot answers.

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?

The description gives clear usage context: it is 'Built for Aztec sign detail pages, day sign cards and chatbot answers about a single Mexica sign.' This implies it should be used for single-sign lookups rather than list-level endpoints. It does not explicitly name alternatives like get_mesoamerican_astrology_aztec_day_signs for multi-sign queries, so it stops short of a full when-not-to-use statement.

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