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

With no annotations provided, the description carries the full burden. It discloses key behavioral traits: the result is deterministic, identical for all users, and requires no authentication. This goes beyond the basic 'get' verb and helps the agent understand safety and consistency, though it doesn't mention return format or error handling.

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 description is two short sentences, each adding essential information: what the tool does and two key behavioral characteristics. It is front-loaded with the action ('Get') and contains zero fluff or repetition.

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?

Given the tool's simplicity (one optional parameter, no output schema, no annotations), the description sufficiently covers purpose, determinism, user consistency, and authentication requirements. It doesn't detail the exact return format, but 'Get the word' implies the outcome, and no output schema exists to specify further. Overall, it's complete enough for an agent to invoke it correctly.

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 input schema already has 100% coverage for the single optional 'date' parameter, describing it as an ISO date defaulting to today. The description reinforces the relevance of the date ('on a given date') but adds no new semantic details beyond the schema, hence the baseline score of 3.

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 clearly states the tool's function: 'Get the deterministic word of the day.' It identifies the specific resource (word of the day) and verb (get), and distinguishes it from sibling tools like lookup_word by emphasizing the deterministic, date-based nature.

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 provides clear context for when to use the tool (to retrieve the word of the day for a given date) and even notes it's the same for all users, which clarifies its utility. However, it doesn't explicitly mention alternatives or when not to use it, so it stops short of a 5.

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