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

With no annotations, the description carries the full burden and does meaningful work: it discloses that this is a paid call ($0.002 USDC via x402 on Base), that the result is persisted server-side, and that it is signed. It stops short of disclosing idempotency (what happens if the same hash is stamped twice), failure/refund behavior on payment errors, or any rate limits.

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: the first gives purpose plus the full return-field set, the second gives cost and payment rail. Nothing is padded and the most decision-relevant facts (what it does, what it returns, what it costs) are front-loaded.

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?

With no output schema, the description usefully enumerates the receipt fields and the verify URL, so an agent knows what comes back. Inputs are fully covered by the schema, and the payment requirement is stated. The gaps are edge-case behavior (duplicate stamping, payment failure) rather than anything blocking a correct call.

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 100% and the schema already specifies the 64-hex-char digest format, optional 0x prefix, and the label's 120-char limit and forbidden '|'. The description adds no parameter-level meaning beyond the schema, so the baseline of 3 applies.

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 precise verb+resource ('Timestamp a SHA-256 hash') and immediately enumerates the artifact produced (a stored, server-signed receipt with named fields). It never names its closest sibling notary_time, so the boundary between 'stamp this hash' and 'get current time' is left implicit rather than stated.

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 purpose implies when to call it (you need proof a hash existed at a moment in time), and the price line adds a real precondition. However there is no explicit 'use this instead of notary_time when...' routing and no statement about when not to use it or how to verify an existing receipt.

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