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

Annotations already declare readOnlyHint=true, so safety is covered, but the description adds genuinely new context: it is free (no credit spend), and it discloses the returned fields per entity type plus that 'recent changes detected' are included. It stops short of saying what window 'recent' covers or whether results are paginated.

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?

A single sentence, front-loaded with the action and resource before the parenthetical detail about returned fields. It is slightly dense but every clause (data fields, changes, cost) carries information an agent would otherwise have to guess.

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 correctly compensates by enumerating return contents per entity type, and it flags the free cost. For a zero-parameter read tool this is nearly complete; only the definition of 'recent changes' and any result limits are left unstated.

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?

The tool takes zero parameters, so the baseline is 4. There is nothing in the schema for the description to clarify, and it does not need to.

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 ('Show') and resource (the user's watched Amazon products and Shopify stores) and enumerates exactly what each entity returns, so an agent knows precisely what comes back. It does not explicitly name watch_add/watch_remove or amazon_product as alternatives, so differentiation is implied by the word 'watching' 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?

Usage is only implied: the agent can infer this is the read counterpart to watch_add/watch_remove. There is no explicit when-to-use or when-not-to-use guidance, and no comparison against amazon_product for users who want product data outside a watch list. The trailing 'Free.' is a useful cost signal but not usage direction.

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