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

With no annotations, the description carries the full burden and does well: it discloses the $0.07 USDC on Base cost, that payment is in-band via x402 (_meta "x402/payment"), that a day pass can bypass per-call payment, and gives the equivalent REST URL. It does not state failure/402 behavior or what the snapshot records contain.

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 dense sentences, front-loaded with the resource description before payment mechanics and the mirror endpoint. Every clause carries information; nothing is redundant, though the URL is arguably listable-only.

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 3-param paid tool with no output schema and no annotations, the description covers scope, cost, payment path and the pass alternative — the main things an agent needs to call it correctly. The remaining gap is return-shape and per-call payment failure handling.

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 33% — only 'pass' is documented in the schema, and the description adds nothing about it beyond what is there. The description does partially compensate for the undocumented 'symbol' (one coin) and 'weeks' (up to 52 weeks), but gives no default, no format hints beyond the schema pattern, and no explanation of what a week's snapshot contains.

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 resource and scope: 'Weekly value-capture snapshots for one coin, up to 52 weeks.' That distinguishes it from get_value_score and get_value_screen by cadence and scope, though it doesn't name those siblings explicitly.

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?

Usage must be inferred: the agent learns it is a per-coin, up-to-a-year history endpoint, which implies 'use when you need time series rather than a point score.' There is no explicit when-to-use or when-not-to-use statement relative to get_value_score or get_history.

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