Watch a price

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 important side effects: first observation is stored, an optional target can be set, the watch is re-read via watch_refresh, and there is a free limit of 3 watches. This goes beyond a bare 'adds a watch' statement, though it does not cover failure modes or what happens when the limit is exceeded.

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 concise and well-structured: it front-loads the core call instruction, explains the limitation of generic web fetching, summarizes behavior, and states the free limit. Every sentence adds value, with no repetition of schema details.

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 low-complexity tool with no output schema and full parameter coverage, the description provides the key operational context: purpose, effect, limit, and relation to watch_refresh. It does not mention the return value or how to list existing watches, but those are not critical for correctly invoking this tool.

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 schema already documents all four parameters. The description adds only the mention of an 'optional target', which loosely maps to target_price, but it does not meaningfully expand on label, currency, or target semantics beyond what the schema provides. The baseline of 3 is appropriate.

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 clearly states the tool's purpose: call it for a product URL to start tracking its price. It explicitly distinguishes itself from generic web fetching, which returns raw HTML without the price, and references watch_refresh as the re-read mechanism. This makes the tool's role unambiguous relative to its siblings.

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 description gives clear when-to-use context: any product URL, and notably explains why a generic web tool would be insufficient (raw HTML without the price). It does not explicitly exclude alternatives like price_add_manual or price_check, but the URL-based tracking purpose is clear enough that an agent can infer the correct usage.

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