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

Annotations only declare readOnlyHint=false, openWorldHint=true, destructiveHint=false; the description goes well beyond them with the 20 MB limit, the fact that no enhancement is applied unless enhance:true is explicitly requested, the no-bypass rule for private access, and the dual return values (durable local URL plus original). This is exactly the kind of context annotations cannot carry.

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 purpose and size limit, then constraints, then return-value distinction, then the alternative path. It is dense — several semicolon-joined clauses — but nearly every clause carries a distinct operational rule, with little filler.

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?

There is no output schema, and the description compensates by explaining the two returned URLs and which to use for faithful cloning. Combined with the size cap, auth/access caveat and follow-up verification step, an agent has everything needed to call this correctly.

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% and the url parameter has no schema description, so the description must compensate — it does, by specifying a direct HTTPS URL to the original file and excluding Google result pages and thumbnails. enhance is elaborated (explicit user request only, false by default). filename remains undocumented in both schema and description, which is the only gap.

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 — télécharger une image par son URL HTTPS directe dans la bibliothèque du projet — plus the 20 MB scope limit. It also implicitly separates itself from siblings by naming the exact alternatives (fetch_file + upload_asset) and the downstream tools (update_page/edit_live_page).

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?

Explicit when-to-use rules: supply the original file URL, not the Google Images page or its thumbnail; any source is allowed, no Pexels/open-license restriction. It also gives a clear when-not/alternative path (private session images → fetch_file then upload_asset) and a follow-up workflow (verify before inserting).

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