contacts_get_avatar

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

Annotations already declare readOnlyHint, destructiveHint=false, and openWorldHint. The description adds real behavioral detail beyond that: the file is saved locally and its path returned, images are also shown, and gRPC returns bytes in-band while REST/socket fetches them from provider storage. That transport-dependent return behavior is genuinely useful and not derivable from the annotations.

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 resource is front-loaded, but the first sentence is a semicolon-joined fragment mixing the noun phrase with an HTTP path, and the transport sentence is dense and hard to parse. Nothing is egregiously wasteful, but the structure is muddled rather than crisp.

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?

There is no output schema, but the description does cover the return shape (local file path, image display) and transport differences. It omits failure behavior, e.g. what is returned when a contact has no avatar. Adequate but with clear remaining gaps.

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 0%, so the description carries the full burden for two required parameters (channelId, contactId). It hints at the contact via 'a contact's avatar' but says nothing about what channelId identifies, how the two relate, or the expected ID format beyond the schema examples. Compensation for the coverage gap is minimal.

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 opening clause 'A contact's avatar, described' is a noun fragment rather than a verb+resource statement, though the surrounding text makes clear it fetches a contact's avatar and returns/saves the file. It implicitly distinguishes itself from the sibling chats_get_avatar by operating on contacts, but never says so explicitly. The purpose is inferable rather than stated.

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?

There is no when-to-use guidance, no prerequisites, and no reference to alternatives such as chats_get_avatar or storage_get. An agent must infer from the name alone whether this is the right avatar-retrieval call. Transport notes are not usage guidance.

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