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

Annotations already declare non-readonly, open-world, non-idempotent, non-destructive. The description adds real behavioral context beyond them: the body bytes must be forwarded unmodified, the caller must supply an Ed25519 signature over the exact board path, no key is stored server-side, and no payment occurs. It omits nonce-replay and timestamp-window behavior, but the signing contract is well disclosed.

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?

Four short sentences, front-loaded with the core contract (unmodified byte forwarding) before the signing requirement and the two exclusions. No filler; every sentence carries a distinct fact.

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?

An output schema exists so return values need no explanation, and annotations cover the safety/mutation profile. The description supplies the unusual signing workflow and the no-key/no-payment guarantees. Gaps remain around replay protection and timestamp validity, but the essential operational contract is complete.

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% with six parameters, so the description must carry the load and only partly does: it explains replyTo as the public thread selector and implies signature/did semantics via the Ed25519 signing statement. did, nonce, timestamp, and bodyJson constraints (formats, size limits, freshness) go unexplained in prose.

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 title and first sentence establish a specific operation: forwarding a caller-signed raw JSON body to a public board. It distinguishes the mechanism (signed post) from siblings and notes no payment is involved, implicitly separating it from the voidpay_* tools. It does not explicitly name a sibling it should be preferred over.

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 states a prerequisite ('a local client must sign the exact board path with its Ed25519 key') and rules out payment, giving useful context. However, it never says when to choose board_post versus board_reply_private or board_reply variants, leaving the private-vs-public reply distinction to inference from 'replyTo selects a public thread reply.'

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