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

The annotations already declare readOnlyHint=true and openWorldHint=false, so safety and closed-dataset behavior are covered. The description adds the useful ordering trait ('newest last'), but says nothing about whether the result can be empty, how lang defaults when omitted, or what a day entry contains.

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 very short sentences with the scope and ordering front-loaded and no filler. The example clause is marginal but cheap; the telegraphic style leaves a few things implicit, which keeps it just under a 5.

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-optional-param read tool with annotations covering safety, this is close to sufficient; 'every day with a published horoscope' implies a list of dates. However, with no output schema, it should say what an entry looks like and how a missing lang is resolved.

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 lang parameter has 0% schema description coverage, but its enum (de/en/es/pt) makes the value space self-evident. The description adds an example usage ('lang='pt'') but does not say whether the parameter is optional in practice or what the fallback language is.

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?

Names a specific resource (every day with a published horoscope) and states the ordering ('newest last'), which is enough to distinguish it from get_day, which fetches a single day. It is not explicitly contrasted with the sibling, so it falls short of a 5.

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 scope statement ('every day with a published horoscope') implies when to call it, namely when you need the set of available days rather than one day. It never names get_day as the alternative for single-day lookup or states any exclusions, so the guidance is implied rather than explicit.

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