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

With no annotations provided, the description carries full transparency responsibility. It discloses supported algorithms, explicitly excludes SHAKE due to XOF nature, specifies key and plaintext length limits, output structure, and default behavior. However, it does not reconcile contradictions with the input schema (e.g., key_in_hex length references AES keys; required_hash_modes default includes Shake values), which slightly undermines transparency.

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 well-structured with sections for algorithms, parameters, output, and typical uses. It is succinct, front-loaded with the main purpose, and every sentence adds necessary detail without redundancy.

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 no output schema, the description thoroughly explains the return format (Results dictionary with hmac_sum_in_hex and hmac_length). It covers algorithm constraints, input limits, defaults, and use cases. Minor omissions include error handling and explicit clarification of schema conflicts, but the description is sufficiently complete for agent invocation.

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%, but the schema descriptions are partly misleading (e.g., key_in_hex referencing AES key sizes, default array containing Shake128/256). The tool description corrects these by providing accurate constraints (16~256 bytes, 1B~16MB, default all 6 algorithms) and adds output semantics. It adds value beyond the schema, though it could more explicitly call out the schema discrepancies.

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 opens with '计算 HMAC（基于哈希的消息认证码）' – a specific verb and resource that clearly defines the tool's function. It further enumerates supported algorithms and typical use cases, distinguishing it from sibling tools like hash_sum (plain hashing) and other cryptographic primitives.

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 contexts for use ('消息完整性验证、API 签名、密钥确认'), but it does not explicitly name alternatives or state when not to use the tool. The use cases are enough to guide an agent, yet the lack of explicit exclusions keeps it from a 5.

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