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

Goes well past the annotations: it discloses case-insensitive name matching with ambiguity refusal that names both ids, per-address link issuance, the 'kept' vs reissued link distinction, that reissue stops the old link (consistent with destructiveHint=true), and the critical fact that no mail is sent by the system. These are exactly the operational traits an agent cannot infer from the schema.

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-loads purpose and circle selection, and every sentence carries information rather than filler. The dense, idiosyncratic phrasing ('made where the person has none by it', 'Lumman sends invitees nothing') costs some readability, but nothing is redundant.

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 compensates by naming the response fields (circle id, whether it was made, kept vs new links) and the no-email side effect. It leaves out authorization requirements and rate limits, but for a 4-parameter mutation tool this is close to complete.

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 100%, so the baseline is 3, but the description adds real meaning: name-vs-id precedence, case-insensitive matching semantics for name, and that a new address gets its own link while an existing one keeps its link unless reissue is set. Only the addresses/reissue mechanics largely duplicate the schema wording.

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+resource (invite people by address into a circle) and immediately scopes it to 'one of the person's own circles', naming circles_list as the authority for circle ids. An agent can distinguish this from circles_list or circles_free_times_find without opening any schema.

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?

Clear about the id-vs-name selection rule ('an existing one by its id... or one by its name, matched whatever its case') and explicit about what to do afterwards ('hand the links to the person to share, or send each from the person's own mailbox'). It stops short of stating when-not to use it or naming an alternative tool for a different invite path.

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