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

With no annotations, the description carries the burden and does disclose the key behavioral trait: it does not sign, so the agent knows this tool only assembles data and cannot mutate on-chain state. It stops short of error behavior, idempotency, or whether the derivations depend on network/registry state.

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 tight sentences, front-loaded with the primary output, followed by the return contents and the scope boundary. 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?

Given no output schema, describing the returned derivations is valuable, but the description leans on an unexplained external reference ('SPEC §6') and leaves several parameters undocumented. Adequate for the assembly step, incomplete for a 7-parameter 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 description coverage is 43% (lat, lng, owner_pubkey, and subtype are undocumented), and the description adds no input guidance — the derivations it lists are outputs, not parameters. With low coverage the description should compensate but does not.

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 (Build) and two concrete artifacts (a canonical Locus `place` payload and the exact OP_RETURN output script hex), plus named derivations. This clearly separates it from build_mint_payload, which builds a different payload type.

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 draws a workflow boundary ('NO signing — assembly/sign/broadcast stays client-side'), which tells the agent this is a first step, but it never says when to choose it over sibling build_mint_payload or other tools. Usage context is implied rather than stated.

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