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

Annotations only declare the generic profile (write, destructive, idempotent, open-world); the description goes well beyond that by disclosing that the token is stored encrypted, is never returned, that Meta validation rejects only explicit invalid/expired responses, and that a saved token leaves delivery unchecked. That is exactly the non-obvious behavior an agent needs before invoking a write tool.

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?

The core action and input rule are front-loaded in the first sentences, followed by validation and side-effect caveats. It is slightly long at six sentences and the 'does not send a test conversion... prove delivery' clause overlaps with the earlier 'delivery unchecked' statement, but every sentence carries information.

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 still covers the success path (encrypted, never returned) and the failure semantics (invalid/expired rejected), plus the auth/plan prerequisite — sufficient for a 3-parameter write tool. It is only marginally incomplete in not describing what the call returns on success beyond the token itself.

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%, so the description must compensate, and it does: it explains the XOR constraint between capi_token and sealed_capi_token, the raw-vs-sealed distinction, the `tyton_sealed_v1.` prefix, and the Pixel-matching requirement for pixel_id. It stops short of describing the pixel_id numeric pattern or capi_token length bounds, which remain schema-only.

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 ('Saves a Meta Conversions API token for the connected site's current Pixel'), tying it to a precise object rather than a generic save. It is clearly distinct from siblings like setup_tracking, approve_conversion_plan, or verify_install, and an agent can route to it without opening another 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?

Gives concrete preconditions ('Requires a connected site with an active Tyton plan', Pixel ID must match the site's saved Pixel) and the selection rule for the two token inputs ('exactly one of capi_token or sealed_capi_token'). It also enumerates what the tool does NOT do (no test conversion, no activation, no delivery proof), but it never names a sibling to use for those adjacent tasks, so routing is left implicit.

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