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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds one genuinely useful behavioral detail — that using 'signer' causes a live key fetch from the lounge — but says nothing about the response (valid/invalid boolean? error on unknown signer?) or lookup failure behavior.

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 compact, front-loaded sentences with no filler. The key-selection rule (sign_pubkey or signer) is stated immediately after the purpose.

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 5-parameter tool with a nested object, 0% schema descriptions and no output schema, the description covers only the top-level key-selection logic. Missing are which fields belong to which kind, signature format, and what a successful or failed verification returns.

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 0%, so the description must compensate; it does explain the sign_pubkey vs signer tradeoff and the kind enum. But it completely leaves the 'fields' object (13 optional sub-properties, additionalProperties: false) and the signature encoding undocumented, which is the largest semantic gap for this tool.

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+resource (verify an Ed25519 signature) plus the input domain (lounge canonical string with kind post|keys|e2e). It is clearly distinguishable from siblings like signing_string or compute_fingerprint, though it never explicitly contrasts with them.

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?

Given implied usage: call this after building a canonical string with signing_string, supplying either sign_pubkey or signer. However there is no explicit when-to-use/when-not guidance or mention of alternative tools, so the agent must infer the workflow.

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