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

Annotations already declare readOnly=true, destructive=false, openWorld=false, so the safety profile is covered. The description adds genuine value beyond that: newest-first ordering, the per-record field set, the 'nothing is charged' cost model, and free re-reads of previously paid answers. However it introduces a cursor naming mismatch (describes 'next_cursor' while the schema parameter is 'cursor') and says nothing about result volume or default limit behaviour.

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 action and ordering, then the record shape, then parameter notes. The single dense run-on sentence packs a lot but stays readable; a slightly tighter split between 'what it returns' and 'how to page/filter' would help.

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 carries the return-shape burden and does so well by enumerating each field. For a 3-parameter read-only list tool, what an agent needs to call it correctly is nearly all present; only the limit parameter's semantics remain unexplained.

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 only 33%: q is documented in the schema and limit is not documented anywhere. The description usefully restates q's containment semantics and clarifies that the cursor walks toward older entries, which the bare 'cursor' title does not convey. The limit parameter (1-50) receives no explanation of its default or effect, leaving a real gap.

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: 'Lists the account's past fast searches, newest first', and enumerates the fields each entry carries (question, kind, answer, source page, row count, sources). An agent can tell this is the read-back history tool rather than the search executor (search_web) or the individual fetch (get_web_search). It stops short of naming those siblings explicitly.

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 implied rather than stated: 'An answer the account already paid for is read here again without a new search' hints that this replaces re-running a search, and 'next_cursor leads to older searches' implies pagination. But there is no explicit when-to-use-this-vs-search_web/get_web_search guidance and no statement about prerequisites or when the list would be empty.

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