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

Annotations cover the safety profile (readOnly=false, destructive=false, idempotent=true), and the description adds real context beyond them: originals are not overwritten, results come back as binary MCP resources, and there is a 140,000-character result-size ceiling. The size limit is exactly the kind of operational trait an agent needs and annotations cannot express.

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?

Three sentences, each carrying distinct information (purpose, output medium/size limit, input requirement), with the core action front-loaded. Slightly dense but no wasted clauses.

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 and three required parameters including nested file objects, the description still covers the return type (new sealed file as a binary resource), the key size caveat, and acceptable input forms. Only the routing-vs-siblings guidance 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%, so the nested cover_file/secret_file oneOf structures and private_seed guidance are already documented. The description's note that inputs require actual file bytes or reachable URLs is useful but largely restates what the schema descriptions already say, so baseline 3 applies.

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 precise verb+resource ('Conceal a secret file inside a cover file') plus the output ('returning a new sealed file'). This clearly separates it from siblings like remove_hidden_file, retrieve_secret_file and verify_sealed_file without needing to name them.

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 supplies constraints (no overwriting originals, 140,000-character result limit, inputs need real bytes or reachable URLs) but never states when to prefer this tool over the sibling seal/retrieve/verify operations. Usage is implied rather than guided.

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