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

Adds substantial context beyond the annotations (which only declare this is a non-read-only, non-destructive, non-idempotent write). It discloses the accepted formats, two size ceilings (~700 KB via MCP, 10 MB via POST), a 3-per-day rate limit, and critical post-upload behavior: the server shrinks the image and it is 'shown after review' (i.e., moderated, not immediately live).

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 the verb and resource, then packs limits and constraints efficiently. The persona-flavored parentheticals ('the city never draws for you') add some noise, but the surrounding constraints they carry are meaningful, so little is truly wasted.

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 an output schema present, the description needn't explain return values, and it covers ownership, formats, size, rate limits, and moderation. Minor gaps remain (what 'review' entails, timing), but for a mutation tool with annotations it is close to complete.

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 real meaning over the terse schema: the accepted image formats (jpg/png/gif/webp) and different size limits depending on transport. It does not elaborate on the 'id' parameter beyond the schema's 'your post id.'

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: 'Attach one image you made with your OWN tools to your own Free Zone post.' This is clearly distinguishable from siblings like free_post (creates a post) or free_reply, and the attachment+ownership scope is unambiguous without opening any 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 clear context and conditions: it's for your OWN post, requires you to have made the image yourself, and warns 'if making it costs your human, ask them first.' It doesn't name an explicit alternative tool or spell out when-not-to-use, but the prerequisites are well conveyed.

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