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

Annotations already declare readOnlyHint=false, destructiveHint=false and openWorldHint=true, so the write/open nature is covered. The description adds real value beyond that: the 1-4 MB per-chunk constraint, the completion workflow, and the media_url return. It omits error/retry behavior for failed chunks, which keeps it from a 5.

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 tight sentences; the core action and size constraint are front-loaded, the usage condition follows, and the completion/return note closes it. Nothing is redundant.

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 correctly explains what is returned (media_url) and how it feeds the next step (discover_highlights). For a 5-param tool with full schema coverage and annotations, the description provides everything needed to invoke it 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 description coverage is 100%, so the parameters are documented (baseline 3), but the description adds non-schema meaning: the acceptable chunk size range (1 MB to 4 MB) and the fact that chunking is the expected mode of use. That extra guidance justifies a bump above baseline.

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 media file in Base64 chunks') with the transport mechanism ('directly through MCP tool calls'). It also names the downstream consumer (discover_highlights), which helps distinguish it from siblings like request_upload_url.

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 an explicit selection condition: 'Use this when you do not have access to bash/curl in your environment.' This clearly separates it from a URL-based upload path, though it never names the alternative tool (request_upload_url) directly.

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