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

Goes far beyond the sole annotation (idempotentHint=true): states price ($0.002) and that it is charged only on settlement, that failed payments store nothing, 64 KB limit, unencrypted storage, TTL default 3600 / max 604800, overwrite-with-seq-bump, and settlement-gated visibility. It also warns that the box id is the sole credential granting read/list/delete/wait to anyone holding it — a security trait no annotation conveys.

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?

Front-loaded with the core write-and-price fact, then layered behaviors, and every sentence carries non-obvious information. It runs long and the credential warning about read/list/delete/wait partly restates the preceding 'whoever knows the string can read and write it' sentence, a minor redundancy.

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?

No output schema exists, yet the description names the return value (the box id) and its downstream use in free reads. For a paid, credential-scoped write tool it covers cost, durability, expiry, visibility timing, and access risk — everything an agent needs before invoking it.

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?

With 0% schema description coverage, the description carries the load and largely does: 'box' is exhaustively explained across its three modes, 'value' gets size and encryption semantics, 'ttl_seconds' gets default and maximum. Gaps remain — it never states the ttl minimum of 60 or the key/value length bounds enforced by the schema.

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?

Opening sentence gives a specific verb and resource ('Store a value under a key') plus the cost model, which unambiguously separates it from the read-side siblings (get, list, wait) and mutating siblings (delete). The follow-on clauses about overwriting and box namespacing further pin down exactly what kind of write this is.

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 gives concrete selection rules for the 'box' parameter: omit it on a paid call to use your own wallet's box, pass a long random string to open a shared channel, or pass a box_... id to address an existing box. What's missing is any explicit routing advice against siblings (e.g., when to recover a value via get instead of re-putting), so a 4 rather than a 5.

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