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

Annotations already declare readOnlyHint=true and destructiveHint=false, but the description adds substantial extra context: it 'reads or computes only and changes nothing', each call is charged so repeats are not free (which explains the idempotentHint=false), pricing is $0.01/call with 25 free and failed calls free. It also discloses the 100,000-character input cap and UTF-8 vs 0x/hex byte handling. This is behavior an agent cannot get from the structured fields.

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 algorithm list and input modes are front-loaded, and the pricing/safety note is kept to the tail. It is a single dense paragraph with little waste, though the pricing sentence could be tightened since it partially repeats the annotations' implication of a metered tool.

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?

With no output schema, the description covers what is produced (named algorithms plus SRI strings) well enough for an agent to call it correctly, and no nested or enum parameters exist. It stops short of specifying the exact return structure (e.g. a map of algorithm to digest), which would fully close the 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 'text' and 'hex' are already documented in the schema. The description reinforces them ('Hashes UTF-8 text, or 0x/hex bytes with hex=true') and gives a concrete example, but adds no syntax or edge-case detail beyond the schema. Baseline 3 is appropriate.

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 action and resource ('Every common hash of one input in a single call') and enumerates the exact algorithms and output formats produced, including SRI strings. It also distinguishes itself from the sibling 'hash' tool by noting it is 'cheaper than hashing one algorithm at a time', so an agent can choose between them without opening either schema.

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?

It gives concrete usage contexts ('checksums, cache keys, file integrity and comparing digests across systems') and points at the single-algorithm alternative implicitly. What is missing is an explicit when-not clause, e.g. use plain 'hash' if you need one digest and want to avoid cost, though the cost note partially covers this.

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