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

Annotations already declare readOnly=false, idempotent=true, and destructive=false. The description adds meaningful behavior beyond that: omitted fields are left unchanged, so it is a partial update, and retention/deletion are deliberately excluded. It does not discuss permissions or rate limits, but it adds solid context for a mutation.

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 short sentences with no waste. The main action is front-loaded, followed by omission semantics and then scope exclusions. Every sentence earns its place.

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 is simple, has full schema coverage, annotations, and an output schema, so the description does not need to explain return values. It covers the mutation semantics and excluded operations well. It could mention permission requirements, but for this tool the description is nearly complete.

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 schema already documents name, color, and source_id. The description restates that name and color can be changed and clarifies omitted fields are preserved, but it adds no syntax or format details beyond the schema. The baseline of 3 is appropriate.

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 states a clear verb and resource: rename a source or change its badge color. It also explicitly scopes out retention and deletion, which helps an agent avoid misfires. However, it does not name or differentiate itself from MCP siblings such as create_source or list_sources.

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?

It gives a clear when-not condition: retention and deletion are not available here and must be done in the web UI. It also implies when to use it, for renaming or recoloring. It stops short of naming sibling tools as alternatives, but the exclusion guidance is explicit and useful.

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