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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is covered. The description adds real value beyond that by enumerating the supported algorithms (the schema's 'algorithm' property has no enum) and disclosing the 1-credit cost, though it says nothing about output format or failure modes.

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?

Two short sentences that front-load purpose and then the algorithm support list. The only waste is the redundant 'HMAC Generator: HMAC Generator' restatement of the title, which adds no information.

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 need not be explained, and annotations carry the safety profile; the description fills the remaining gaps with algorithm support and cost. For a single-purpose crypto utility, nothing needed to invoke it correctly is missing.

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 would be 3, but the description goes further by listing the accepted algorithm values (SHA-256, SHA-384, SHA-512, SHA-1, MD5), which the schema leaves unenumerated. It adds nothing about the encoding or secret parameters, but those are already documented.

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 Hash-based Message Authentication Codes') and names the supported digest algorithms. It does not, however, distinguish itself from nearby siblings like HashGenerator, MurmurHash, or TOTPGenerator, so the keyed-vs-unkeyed distinction must be inferred.

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 phrase 'for data integrity and authentication' gestures at purpose but gives no explicit when-to-use guidance, no prerequisites, and no named alternative such as HashGenerator for non-keyed hashing. The agent must decide on its own when this tool beats its siblings.

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