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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is fully covered. The description adds only 'same as the app shows today', giving no extra behavioral context such as return shape, ordering, or behavior when the date has no reading.

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?

The first sentence is a tight, front-loaded statement of purpose, but the second sentence is app-level marketing ('plans, search, and the whole Theogony, Iliad, Odyssey and Poetic Edda') that says nothing about invoking this specific tool and does not earn 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 zero-required-parameter, read-only lookup with full schema coverage and no output schema, the definition is adequate but minimal. It leaves the return structure (what 'line by line' actually yields) and the no-reading-for-date edge case unaddressed.

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 single 'date' parameter already has complete schema documentation including the YYYY-MM-DD format and UTC default. The description adds nothing about the parameter, so the schema does all the work — the baseline for 100% 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 states a concrete verb+resource: it returns today's reading 'line by line', matching what the app displays. However, it never distinguishes itself from the sibling tools get_reading or list_readings, which a 'today's reading' tool arguably overlaps with.

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 statement of when to use this versus get_reading, get_card, or list_readings; the only usage cue is implicit in the name 'get_today'. The second sentence describes the app's overall content rather than when this tool applies.

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