URL: https://gofastmcp.com/servers/transforms/resources-as-tools
Title: Resources as Tools - FastMCP

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Basic Usage
Static Resources vs Templates
Reading Resources
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Resources as Tools
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Expose resources to tool-only clients
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New in version
3.0.0
Some MCP clients only support tools. They cannot list or read resources directly because they lack resource protocol support. The
ResourcesAsTools
transform bridges this gap by generating tools that provide access to your server’s resources.
When you add
ResourcesAsTools
to a server, it creates two tools that clients can call instead of using the resource protocol:
list_resources
returns JSON describing all available resources and templates
read_resource
reads a specific resource by URI
This means any client that can call tools can now access resources, even if the client has no native resource support.
​
Basic Usage
Pass your FastMCP server to
ResourcesAsTools
when adding the transform. The generated tools route through the server at runtime, which means all server middleware — auth, visibility, rate limiting — applies to resource operations automatically, exactly as it would for direct
resources/read
calls.
ResourcesAsTools
(and
PromptsAsTools
) should be applied to a FastMCP server instance, not a raw Provider. The generated tools call back into the server’s middleware chain at runtime, so they need a server to route through. If you want to expose only a subset of resources, create a dedicated FastMCP server for those resources and apply the transform there.
from
fastmcp
import
FastMCP
from
fastmcp
.
server
.
transforms
import
ResourcesAsTools
mcp
=
FastMCP
(
"
My Server
"
)
@
mcp
.
resource
(
"
config://app
"
)
def
app_config
()
->
str
:
"""
Application configuration.
"""
return
'
{"app_name": "My App", "version": "1.0.0"}
'
@
mcp
.
resource
(
"
user://
{user_id}
/profile
"
)
def
user_profile
(
user_id
:
str
)
->
str
:
"""
Get a user's profile by ID.
"""
return
f
'
{{
"user_id": "
{
user_id
}
", "name": "User
{
user_id
}
"
}}
'
# Add the transform - creates list_resources and read_resource tools
mcp
.
add_transform
(
ResourcesAsTools
(
mcp
))
Clients now see three tools: whatever tools you defined directly, plus
list_resources
and
read_resource
.
Both generated tools are annotated with
readOnlyHint=True
, since they only read data. Clients that respect tool annotations (like Cursor) can use this to auto-confirm these tool calls without prompting the user.
​
Static Resources vs Templates
Resources come in two forms, and the
list_resources
tool distinguishes between them in its JSON output.
Static resources have fixed URIs. They represent concrete data that exists at a known location. In the listing output, static resources include a
uri
field containing the exact URI to request.
Resource templates have parameterized URIs with placeholders like
{user_id}
. They represent patterns for accessing dynamic data. In the listing output, templates include a
uri_template
field showing the pattern with its placeholders.
When a client calls
list_resources
, it receives JSON like this:
[
{
"
uri
"
:
"
config://app
"
,
"
name
"
:
"
app_config
"
,
"
description
"
:
"
Application configuration.
"
,
"
mime_type
"
:
"
text/plain
"
},
{
"
uri_template
"
:
"
user://{user_id}/profile
"
,
"
name
"
:
"
user_profile
"
,
"
description
"
:
"
Get a user's profile by ID.
"
}
]
The client can distinguish resource types by checking which field is present:
uri
for static resources,
uri_template
for templates.
​
Reading Resources
The
read_resource
tool accepts a single
uri
argument. For static resources, pass the exact URI. For templates, fill in the placeholders with actual values.
# Reading a static resource
result
=
await
client
.
call_tool
(
"
read_resource
"
,
{
"
uri
"
:
"
config://app
"
})
print
(
result
.
data
)
# '{"app_name": "My App", "version": "1.0.0"}'
# Reading a templated resource - fill in {user_id} with an actual ID
result
=
await
client
.
call_tool
(
"
read_resource
"
,
{
"
uri
"
:
"
user://42/profile
"
})
print
(
result
.
data
)
# '{"user_id": "42", "name": "User 42"}'
The transform handles template matching automatically. When you request
user://42/profile
, it matches against the
user://{user_id}/profile
template, extracts
user_id=42
, and calls your resource function with that parameter.
​
Binary Content
Resources that return binary data (like images or files) are automatically base64-encoded when read through the
read_resource
tool. This ensures binary content can be transmitted as a string in the tool response.
@
mcp
.
resource
(
"
data://binary
"
,
mime_type
=
"
application/octet-stream
"
)
def
binary_data
()
->
bytes
:
return
b
"
\x00\x01\x02\x03
"
# Client receives base64-encoded string
result
=
await
client
.
call_tool
(
"
read_resource
"
,
{
"
uri
"
:
"
data://binary
"
})
decoded
=
base64
.
b64decode
(
result
.
data
)
# b'\x00\x01\x02\x03'
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