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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds valuable behavioral details: splitting at spaces where possible in length mode, interpreting \n and \t in delimiter mode, and returning a list of blocks. This goes beyond the schema and gives the agent a clear model of how the tool behaves.

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?

Four concise sentences, front-loaded with the primary purpose, followed by mode details and return type. No redundant or irrelevant content; the source URL is a minor but non-intrusive addition. Every sentence earns 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 text-splitting tool with schema covering all parameters and an output schema implied, the description is sufficiently complete. It explains both modes, the numbering option, delimiter escaping, and return value. Edge cases like empty text or oversized words are not covered but are minor for this utility. Annotations already handle the operational safety context.

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 the baseline is 3. The description adds meaning by explaining how mode affects splitting behavior and that numbered creates '1/n' suffixes in length mode. It also clarifies the delimiter special-character interpretation, reinforcing and slightly expanding on the schema descriptions.

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 purpose: 'Split a long block of text into smaller blocks.' It then details two specific modes (length and delimiter), making it distinct from sibling text tools like hopi_character_counter or hopi_word_counter. The verb 'split' and resource 'text' are explicit and unambiguous.

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 on when to use the tool—whenever text needs to be split into smaller blocks—and explains the two operational modes, guiding which parameters to use. It does not explicitly name alternatives or exclusions, but the purpose is so specific that no close sibling alternatives exist among the listed tools.

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