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

Annotations already indicate readOnlyHint=false, destructiveHint=false, and idempotentHint=false. The description adds that the tool returns a 'durable Postly media object and upload usage details,' which is useful context. However, it does not disclose potential side effects like storage costs, rate limits, or whether the media is immediately accessible. It doesn't contradict annotations, but adds only modest behavioral context beyond them.

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?

The description is a single, front-loaded sentence that states the purpose, lists supported input formats, and describes the return value. Every phrase earns its place; there is no redundant or vague wording. This is a model of concise, informative tool documentation.

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?

The tool has 6 parameters, one nested object, and an output schema. The description covers the core behavior (import media, return durable object and usage details) and input modes. It doesn't explain return format details, but the output schema exists to provide that. Given the complexity and existing structured metadata, the description is complete enough for an agent to use 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?

The schema has 100% description coverage for all parameters, so the baseline is 3. The description adds a compact summary of input types ('client-provided file reference, URL, data URL, or base64 payload') and mentions that file_name is required for base64/data, but these details are already in the schema. The description adds no further meaning beyond what the schema already provides.

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?

The description clearly identifies the tool's function: 'Imports media into Postly storage independently of a post mutation.' It specifies the resource (Postly media storage) and the action (upload/import), and lists accepted input forms (file reference, URL, data URL, base64). This distinguishes it from sibling tools like postly_create_post or postly_update_post, which focus on post mutations.

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?

The phrase 'independently of a post mutation' establishes a clear usage context: this tool is for uploading media that may later be attached to a post. It implies it should be used when you need a durable media object before creating or updating a post. While it doesn't explicitly name alternatives (e.g., embedding media directly in a post mutation), the context is sufficient for an agent to understand when to invoke it.

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