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

With no annotations provided, the description carries the full behavioral disclosure burden. It explicitly reveals rate limiting, content acceptance criteria, refusal behavior that names the violated rule, immutability of written lines, and the absence of an account requirement. This is strong transparency for a mutation-style tool.

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?

The description is compact and front-loaded: it states the core action first, then constraints, then behavioral guarantees, then access requirements. Every sentence contributes meaningful information with no filler or redundant restatement of the tool name.

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 simple three-parameter write tool with no annotations and no output schema, the description covers the essential invocation contract: signing, content limits, rate limit, screening, and immutability. It does not describe the success return value or explicitly point to read_rules for the poison rules, but those are not necessary for correct invocation.

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?

The input schema already provides 100% coverage with exact formats for line, pubkey, and signature. The description adds useful supplementary meaning by specifying printable text, the per-key-per-hour limit, and the requirement that the line must be signed with an ed25519 key, which goes slightly beyond the schema alone.

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 uses a specific verb and resource: "Leave one line on the wall" clearly identifies a write action to the wall. It distinguishes itself from siblings like wall_read and letter_write by emphasizing the wall context, the signed line, and the append-only semantics.

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?

The description gives useful constraints such as one line per key per hour, printable text, and poison-rule screening, but it does not explicitly say when to prefer this tool over named alternatives like letter_write. Usage is implied strongly by the name and action, but no direct when-to-use or when-not-to-use guidance is provided.

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