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

Annotations already declare readOnlyHint, openWorldHint, and destructiveHint, so safety is covered. The description adds genuinely new context beyond them: the 1-credit cost, the 26-character fixed length, the collision-resistant guarantee, and the chronological ordering property. The phrase 'with format details' is vague and does not say what those details are.

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?

Three sentences, front-loaded with the core capability and the cost note last. The opening repeats the tool name twice ('ULID Generator: ULID Generator') and the trailing 'with format details' is filler, but the description is otherwise dense and free of padding.

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?

A simple two-optional-parameter generator with full schema coverage, annotations, and an output schema, so little needs explaining. The description supplies credit cost and ID characteristics; only the vague 'format details' claim and the absence of sibling routing leave a small gap.

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 both 'count' and 'timestamp' are already documented with defaults and examples. The description only restates that both are optional, an integer millisecond timestamp, and a batch count; it adds no format or constraint information beyond the schema, so the baseline 3 applies.

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?

States a specific verb and resource ('creates Universally Unique Lexicographically Sortable Identifiers') and explains the key differentiating property, chronological sortability. It does not explicitly name the closely related siblings UUIDGenerator, GUIDGenerator, or CuidGenerator, so an agent must infer the distinction from the acronym expansion.

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 only implied: 'order records chronologically' hints at when sortable IDs matter, but there is no explicit when-to-use or when-not-to-use guidance, and no routing to UUIDGenerator or CuidGenerator for non-sortable or short-ID needs. The default of a single ID is left to the schema rather than stated.

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