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

With zero annotations, the description carries the full behavioral burden and does it well: it discloses that the operation is free, that it mutates state, that it requires owner-signed EIP-191 personal_sign auth, and that ts is time-limited to 5 minutes — which reveals replay protection behavior. It stops short of describing failure modes on bad signatures, but covers the critical non-obvious behaviors.

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?

Three sentences, zero filler. The main purpose is front-loaded, followed by cost/auth context, then the time constraint. Every sentence earns its place and the ordering matches the likely decision sequence for an agent.

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 mutation tool with 6 parameters, no annotations, and no output schema, the description covers the essential non-obvious ground: ownership, signature flow, cost, and time sensitivity. The only notable gap is that the canonical signed-message format is deferred to the wall README, and there is no response/return guidance — minor for a mutation whose behavior is otherwise well-scoped.

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 only 50%, so the description must compensate. It adds real meaning: ts gains a freshness window, signature gains the canonical-message and owning-wallet context, and the otherwise-undocumented link/message/pixels parameters gain semantic grouping via 'repaint pixels or update message/link.' This meaningfully bridges the coverage gap, though coord-specific format details remain schema-only.

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 opens with a specific action pair — 'Repaint pixels or update message/link on a block you own' — naming the verb, resource, and ownership constraint in one sentence. This cleanly distinguishes set_pixels from read-only siblings (get_block, get_wall) and from buy_block, which is the acquisition tool.

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 ownership precondition is explicit ('on a block you own', 'wallet that bought the block'), which tells the agent when this tool is applicable. It does not name sibling alternatives or state when not to use it, but the context is clear enough that an agent can infer the workflow: own a block first, then repaint it.

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