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

Adds real behavioral context beyond the annotations: no network access, no stored state, determinism, and concrete limits (64 KB input, 1 s per call). Minor internal inconsistency: the schema allows data up to 1,048,576 bytes while the description caps JSON input at 64 KB, so an agent could hit an undocumented ceiling.

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?

Front-loaded with the algorithm specification and broken into labeled clauses (When / Not for / Side effects / Deterministic / Limits), which is easy to scan. Length is inflated roughly 2x by the full ES+EN duplication, though that appears to be an intentional localization convention.

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 two-parameter pure function this covers everything an agent needs: algorithm identity, when to prefer it, what it is not, side-effect profile, determinism, and resource limits. An output schema exists and the input schema fully documents both parameters, so no return-value prose is required.

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 of 3 applies. The description adds no parameter-level detail — notably it never mentions input_encoding (utf8/hex/base64), which is the one parameter where a mistake would silently produce a wrong checksum.

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?

Names the exact algorithm and variant (CRC-16/CCITT-FALSE, poly 0x1021, init 0xFFFF, no reflection) rather than just 'checksum', and states it is non-cryptographic. An agent can distinguish this from checksum-crc32, checksum-adler32 or checksum-xxh32 without opening the 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?

Provides an explicit 'When' clause (fast non-cryptographic error detection, sharding, hash tables) and an explicit 'Not for' clause naming checksum-crc32. It does not, however, help choose among the other eight checksum siblings (adler32, fnv1a32/64, murmur3-32, xxh32, crc32c), which is the harder routing decision.

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