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

With no annotations, the description carries the full burden of behavioral disclosure. It reveals that the scan runs asynchronously ('Returns { jobId, jobToken } in milliseconds — the scan itself runs behind it'), that omitting birthdayHeight triggers a backward walk that is 'slower but always correct', and that the tool is 'FREE and rate-limited (20 scan starts / 15 min, shared across all agents)'. These are critical operational traits an agent must know.

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?

The description is four sentences, front-loaded with purpose and return value, and each sentence adds essential context: async behavior, birthdayHeight nuance, rate limits, and alternatives. There is no fluff or repetition; the use of capitalization for 'BACKWARDS' and 'FREE' draws attention to key points.

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 there is no output schema, the description sufficiently explains the return shape and asynchronous workflow. It also covers rate limiting, polling, and when to use paid alternatives, making it complete for an agent to invoke the tool correctly. It points to the relevant sibling (scan_status) for follow-up, so the agent knows the full lifecycle.

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%, so the baseline is 3. The description adds meaning beyond the schema by clarifying the birthdayHeight trade-off: 'Omitting birthdayHeight makes the scanner walk BACKWARDS from the chain tip to find the wallet's first note, which is slower but always correct.' This helps the agent reason about the parameter without opening the schema. It doesn't repeat all parameter details, so 4 rather than 5.

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 'Open a scan of a Zcash UFVK' – a specific verb and resource that clearly distinguishes this from sibling tools like seneschal_zecmon_scan_status and seneschal_zecmon_scan_cancel. It also states the immediate return value, making the tool's core function unmistakable.

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?

Explicitly tells when to use this tool vs alternatives: 'poll seneschal_zecmon_scan_status' for the result, and 'For anything scheduled, bulk or latency-sensitive use ... private/historical ... or private/info to get a webhook instead of polling at all.' It also warns about the shared rate limit, helping the agent decide if this is the right tool for the job.

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