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

Goes well beyond the annotations (readOnlyHint=false, openWorldHint=true) by disclosing auth requirements ('Requires a bearer token'), a non-idempotency/retry warning ('Do not retry'), a rate constraint (daily visit count), a content restriction (don't list wherewasai.com), and a side effect ('It is dropped automatically'). These are exactly the behavioral traits an agent needs before invoking a mutation.

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 built from short, mostly purposeful sentences. The trailing 'It is dropped automatically' is ambiguous about its referent and slightly muddies an otherwise efficient structure.

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 two-parameter mutation with no output schema, the description covers auth, retry policy, rate limits, and content rules, which is enough to call it correctly. It could be tighter about what happens after posting, but nothing essential is missing.

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% and both parameters are already documented, so the baseline is 3. The description's 'domains is the ordered list' and 'note is optional' largely restate the schema, adding only mild emphasis on ordering.

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: 'Post one postcard for this visit.' An agent can distinguish it from the read-oriented sibling recent_postcards. However, it never names a sibling or explicitly frames itself as the write counterpart to the listing tools, 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?

The description gives operational constraints ('Do not retry', 'Posting here already means you visited') but never states when to choose this over alternatives like recent_postcards or request_certification. Usage is implied by 'for this visit' rather than explicitly routed.

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