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

Annotations cover safety (readOnlyHint=false, idempotentHint=true, destructiveHint=false, openWorldHint=true), and the description adds critical operational behavior: what the server does (probes bytes, marks ready), retry semantics using the SAME mediaId, retryAfterSec, and the nextAction field. This is exactly the kind of context annotations cannot provide.

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?

Information-dense with several clauses, but each sentence is actionable: finalization, parameter source, error handling, and workflow routing. The error-code details are front-loaded after the core purpose; a slightly tighter structure could group the retry states, but nothing is 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?

For a single-parameter finalize tool with an output-less response and rich annotations, the description covers purpose, retry semantics, error states, workflow sequencing, and exclusions. An agent has everything needed to invoke and recover 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 coverage is 100% and the single mediaId parameter is fully documented in the schema. The description reinforces its provenance ('from get_upload_url') but adds no syntax or format detail beyond the schema. 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 specific verb (finalize) and resource (uploaded media file) and clarifies the exact precondition (after HTTP PUT to uploadUrl). It is clearly distinguishable from siblings like get_upload_url and attach_media.

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 explicit when-to-use ('Use the mediaId from get_upload_url'), state-specific routing for error codes (MEDIA_UPLOAD_PENDING, MEDIA_VALIDATION_PENDING, retryable=true), and an exclusion ('Not needed for mediaUrls attachments'). It routes the agent to get_post and update_post at the right step.

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