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

Annotations already declare readOnly/idempotent/openWorld=false, and the description goes further with what the check cannot determine ('cannot tell whether it is on-curve, funded or owned'), no network/no stored state, determinism, and explicit limits (64 KB input, 1 s per call, 1 MB result). The on-curve/funded caveat is the kind of semantic boundary an agent would otherwise get wrong.

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 core check and cleanly labeled (Cuándo / No para / Efectos / Determinista / Límites), so scanning is easy. It loses a point for being fully bilingual with the English half repeated verbatim in inputSchema.description, which roughly doubles the token cost for the same 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?

For a single-parameter offline validator with an output schema, annotations and a fully described input, nothing an agent needs is missing: it knows the criterion, the exclusions, the side-effect profile and the operational limits.

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% so the baseline is 3; the description adds real meaning by defining what 'valid' means for this parameter (Base58 over the Bitcoin alphabet decoding to 32 bytes), not just the type and max length the schema already gives.

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 (verify that a string is a syntactically valid Solana public key) plus the exact acceptance criterion: Base58 decoding to exactly 32 bytes. It also explicitly demarcates itself from the closest sibling (bitcoin-address-validate), so an agent can choose 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?

Has explicit 'Cuándo' and 'No para' sections: use it when an identifier's format must be verified offline before use, and do not use it for Bitcoin Base58Check validation, naming the alternative tool. This is exactly the when/when-not/alternative triad.

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