lib_symbol_update_document_source

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

Goes well beyond the annotations: it discloses irreversibility, that no undo exists, that no backup snapshot is taken (because library assets are not documents), the write-permission requirement, and the boolean return. This is exactly the destructive-operation context an agent needs before committing.

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?

Front-loaded with the action, then the irreversibility warning, then the prerequisite and return type. Four tight sentences with no filler; every clause carries actionable information.

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 destructive mutation with no output schema, the description covers the safety posture, the recovery path, the permission prerequisite, and the return value. There is nothing an agent needs to call this correctly that is missing.

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 all four parameters (symbolUuid, libraryUuid, documentSource, instance_id) are already documented in the schema. The description adds no format or syntax detail beyond it, so the 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+resource: 'Replace a library symbol's entire .esym source.' The scope (entire source, symbol-level) is precise and distinguishes it from footprint/document variants and from lib_symbol_get, which it explicitly positions as the read counterpart.

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 clear operating context: it must target a writable library (personal/team/project), and it prescribes the recovery workflow ('Fetch and save the current source with lib_symbol_get first'). It stops short of naming when-to-use alternatives like document_set_source, so an explicit exclusion is missing.

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