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

Annotations already declare a non-read-only, open-world, non-destructive write, and the description adds one genuine behavioral fact: the account's Public Profile is applied automatically, plus that url "overrides the default". It does not disclose permissions needed, whether repeated calls create duplicates, validation failure modes (e.g. headline length rejection), or what is returned for chaining into snapchat_create_ad.

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 tightly packed sentences with the media-source options and the sequencing call-to-action front-loaded; nothing is filler. The colon-and-parenthetical style is dense but readable and every clause 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?

For a 13-parameter mutation tool with no output schema, the description covers the primary creation flow and the handoff to snapchat_create_ad, which is the critical path. It leaves secondary parameters (account selection, folder, language, brand_name, profile_id) and the returned identifier unexplained, so an agent still needs the schema and trial for those.

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?

With 62% schema coverage across 13 parameters, the description meaningfully disambiguates the mutually exclusive media inputs (media_id from chat attachment, media_url, snap_media_id) and restates the 34-character headline limit and the URL/CTA vs plain-Snap-ad choice. It adds no meaning for name, folder, account, language, brand_name, or creative_id, which remain schema-only or undocumented.

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 ("Create a creative") and immediately enumerates the three supported media sources: attached file via media_id, public URL, or Snap media ID. It also names the follow-on tool snapchat_create_ad, so an agent can place it in the campaign-build sequence and distinguish it from snapchat_creatives (listing) and snapchat_create_ad (ad creation).

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?

Explicitly states the next step ("Then use snapchat_create_ad") and clarifies the no-URL path as "a plain Snap ad", which is real when-to-use guidance. It stops short of saying when to prefer media_id vs media_url vs snap_media_id vs the reuse path (creative_id), leaving that inference to the schema.

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