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

Annotations only cover readOnly/destructive/openWorld, so the description carries the real behavioral load and does so well: size cap (2097152 bytes), the two-phase PUT flow with a literal curl example, the need for a follow-up completion call, and the no-delete limitation. It omits permission/auth requirements and what the response contains, but the added behavioral context is substantial.

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 the purpose, then the two flows, then the limitation—a logical order with no filler sentences. It is a single dense paragraph with run-on clauses (multiple semicolons) that hurt scanability slightly.

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 genuinely two-phase upload tool with no output schema, the description explains the mechanics but references three variables (attachToken, uploadURL, maxSize) that appear nowhere in the schema or its own text, so an agent cannot tell how to obtain them. That missing entry point is a real gap despite otherwise rich coverage.

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 relationship semantics the schema lacks: attachToken routes to task/bug/feature specs while fid routes to chat message attachments, and one fid can be attached in several places. The size and base64 details duplicate the schema rather than extend it.

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 ("Uploads a file for attachment") and immediately scopes the two attachment destinations, so an agent knows this creates/stores content rather than retrieving it. It does not name the siblings it must be distinguished from (file_get, file_url), so an agent still has to infer the boundary from context.

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?

Clearly splits the two usage modes: with dataBase64 the file is saved at once, without it any-size uploads go through a PUT to uploadURL followed by a completion call. It also states a hard exclusion ("Files cannot be deleted through MCP"). It never says where attachToken/uploadURL come from or which sibling produces them, leaving the entry condition implicit.

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