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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds genuinely useful context beyond that: Base64 is UTF-8 scoped, and critically that the JWT signature is NOT verified, which prevents an agent from misrepresenting decoded tokens as validated.

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?

One dense sentence lists the operations, followed by a one-line usage directive. Every clause earns its place and the operational scope is front-loaded with no filler.

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 still hints at return shape for JWT (readable exp/iat/nbf dates). Return format for the encode/decode/hash paths and the hash-algorithm selection mechanism remain unstated, leaving a small but real gap for a 6-operation tool.

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 0%, so the description must carry parameter meaning. It clarifies the 'text' payload and maps well to the operation enum values, but it never explains how the hash algorithm (MD5/SHA-1/SHA-256/SHA-512) is selected given that the schema exposes only 'operation' and 'text' — a real ambiguity the description should resolve.

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 names the exact resource (text transforms) and enumerates every supported operation: Base64, URL encode/decode, JWT decode, and four hash algorithms. It is immediately distinguishable from siblings like usesignal_test_regex or usesignal_format_json, and the operations align 1:1 with the schema enum.

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 a direct directive: 'Use this instead of computing hashes or Base64 by hand,' which establishes when to reach for it. It stops short of any when-not guidance or sibling routing, but the siblings are functionally unrelated, so the omission is minor.

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