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

Annotations declare readOnlyHint=false, idempotentHint=false, openWorldHint=true, destructiveHint=false. The description goes beyond them by disclosing the webhook delivery is an HMAC-signed POST, that polling is available via a concrete resource path, and that credentials are required. It omits quota/duplicate-subscription behavior, which a mutating, non-idempotent tool would benefit from.

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 tight sentences; the core action is front-loaded and the delivery mechanics follow. The trailing 'Requires credentials.' is short and earns its place as an operational caveat, though the sentence structure could be marginally tighter.

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, nested query/channels objects, and a non-idempotent mutating operation, the description covers what is needed to call it correctly: what gets saved, where matches go, and that auth is needed. Missing details on duplicate-subscription handling and limits are minor gaps.

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 both the query filter object and the channels array are already well documented in the schema, including the 1-5 constraint and channel types. The description restates the channel options and adds no format or syntax detail beyond the schema, so baseline 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 states a specific verb+resource ('Save a search') scoped to the calling agent principal, and clarifies that new matches are pushed to channels. It does not explicitly name a sibling like search_inventory to distinguish persistence from one-shot search, so it stops short of a 5.

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?

Use is implied: this is the tool for persisting a search and receiving ongoing notifications. However, there is no explicit when-to-use vs when-not guidance (e.g., use search_inventory for immediate results instead of subscribing) and no prerequisites beyond 'requires credentials'.

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