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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds real value beyond that by disclosing the returned field set (there is no output schema) and by defining what a site is in this domain. It does not, however, describe pagination behavior or how many items come back per call, which the schema only partially covers.

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 sentences with no padding: the first front-loads the returned fields, the second supplies domain context and the sibling disambiguation. Both sentences earn their place, though the second is more context than instruction.

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 simple read-only, single-parameter listing tool with no output schema, the description covers the essentials: what is returned, whose sites, and how it differs from ask_site. The remaining gap is pagination behavior, which is mostly carried by the schema's next_offset wording.

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?

There is a single parameter and the schema description coverage is 100%, with the offset parameter fully documented (page of 50, next_offset chaining). The description adds no parameter-level detail, which is acceptable since the schema does the heavy lifting, but it earns only the baseline.

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 enumerates exactly what the tool returns (id, name, status, creation time, document counts, read counts) for the signed-in account, so an agent knows precisely what this list contains. It also draws a line against ask_site by explaining that ask_site answers questions from those documents rather than listing them. It stops short of a verb-led statement of the listing action, but the resource and scope are unambiguous.

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 mention that ask_site answers questions from a site's documents suggests this tool is for enumerating sites, not querying content. There is no explicit when-to-use statement, no mention of when a different listing tool (e.g. search or list_sources) would be preferable, and no stated prerequisites such as needing a signed-in account.

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