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

With no annotations, the description carries the full burden and does so well: login requirement, accepted formats (jpg, png, gif, webp), a 10MB size cap, the exactly-one-of input constraint, and the important caveat that file_path only works for local MCP clients. These are real constraints an agent must know before invoking.

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-loads purpose and return value, then packs constraints into tight clauses with no filler. Every sentence — formats, size, login, source exclusivity — earns its place.

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 supplies the return value (public URL) and its usage, plus all input constraints and auth needs. Nothing an agent needs to call this correctly appears to be 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 baseline is 3, but the description adds genuinely non-redundant meaning: the three image-source parameters are mutually exclusive ('Provide EXACTLY ONE of'), and the file_path/client-mode limitation is reinforced in prose. That constraint is the kind of information a schema alone would not enforce.

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+resource ('Upload an image to Liberty.win') and immediately names the artifact produced ('get a public URL'). This clearly distinguishes it from write-oriented siblings like create_post, whose url field it feeds.

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?

Explains the two downstream uses of the returned URL (post url field, markdown embed) and states the prerequisite ('Requires login'), which gives an agent clear context for when to call it. It doesn't explicitly point to an alternative upload path or say when NOT to use it, but there is no obvious sibling to route against.

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