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

Annotations only flag readOnlyHint=false, openWorldHint=true and idempotentHint=false; the description goes far beyond by disclosing cost ($5/portfolio, per-reference and per-check pricing), purchase semantics ('ONE purchase covers the whole list'), the once-only token, immediate signed first check, daily re-check cadence, and that each change yields a signed receipt while no changes yield no message.

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 purpose and scope, then pricing, then return/receipt details in a logical order. It is dense but nearly every sentence carries new information; the pricing triple ('US$5 a portfolio — 20 cents a reference, under a cent a check') is slightly redundant.

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 compensates by stating what is returned (a read URL and a token shown only once) and what audit artifact accompanies checks (an Ed25519-signed receipt verifiable against a published key). For a paid, non-idempotent watch tool this is close to complete, though it could note anything about token expiry or renewal.

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 100% and both parameters (items, webhook) are already documented, so the baseline is 3. The description adds useful semantics the schema lacks: that a repeated reference is charged once and that webhook posts only fire on recorded changes, plus the 25-item ceiling in prose.

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 and resource with scope: 'Watch a whole list instead of one reference at a time: up to 25 citations or package versions re-checked every day for 30 days under one token.' It also explicitly distinguishes itself from the sibling watch_add, so an agent can route without opening either schema.

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?

Names the alternative and the selecting condition: 'ONE purchase covers the whole list: for a single subject on its own, use watch_add.' The 'whole list vs single reference' split is the exact decision the agent needs to make among these siblings.

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