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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description usefully adds cost ('5 credits, Tier ½') and the endpoint path, but says nothing about permissions, rate behavior, or how the date is resolved. With annotations carrying most of the load, a 3 is fair.

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?

Front-loaded with the core action in the first sentence, with group/endpoint/cost metadata bracketed compactly. No filler, though the parameter detail in sentence two is the part that misfires rather than over-length.

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?

An output schema exists, so return values needn't be explained, and the description covers purpose, endpoint, and cost for a simple zero-required-parameter read tool. The only gap is the mismatch between the described date query and the actual schema parameters.

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 coverage is 100%, so baseline is 3, but the description introduces an 'Optional ?date=YYYY-MM-DD query' that does not appear among the two schema parameters (fields, precision). This phantom parameter can mislead an agent, and the actual schema parameters are never mentioned, so the description adds no useful meaning and introduces confusion.

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 specific verb and resource ('Compute today's personal angel number') and clarifies the derivation ('digit-sum reduced to single digit'), which separates it from the generic angel-number siblings. It does not explicitly name which sibling it differs from, keeping it below 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?

Usage is implied by 'today's' – an agent can infer this is the daily-variant versus the by-life-path/by-number/decode siblings – but no explicit when-to-use, when-not, or named alternative is given. This is minimum-viable context rather than guidance.

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